EVOLUTION OF THE TELLINACEA (BIVALVIA)

The suspension feeding Astartacea appear to be among the earliestheterodonts. These organisms may have given rise to the Carditaceaand the rest of the heterodonts including the Tellinacea. Paleontological evidence indicates that the earliest Tellinaceawere suspension feeders with members that lived vertically ina burrow in shifting sand. These conditions resemble those foundin species of modern Donax in the Donacidae. From a Donax-likestate of suspension feeding evolution most likely proceededto non-selective feeders. Extant organisms that resemble thisstage are found in the Solecurtidae. A later stage resemblessome of the extant Psammobiidae. The final stage in tellinaceanevolution is the acquisition of deposit feeding with its associatedmorphology. These stages are observed in the Scrobiculariidae,Tellinidae and a few members of the Semelidae. (Received 27 April 1981;     

THE MANTLE AND SHELL OF SOLEMYA PARKINSONI (PROTOBRANCHIA: BIVALVIA)

The shell of Solemya exhibits considerable flexibility which is further enhanced by the marked extension of the periostracum beyond the calcareous portions of the valves. This fcature, more than any other, has made possible the habit, unique among bivalves, of burrowing deep within the substrate without direct contact with the water above. The inner calcareous layer of tho valves is restricted to a small area near the umbones while the outer calcareous layer is thin and contains a high proportion of organic material. The shell conchiolin consists mainly of protein, varying in composition, but much of it strengthcned by quinone-tanning, and in ccrtain regions probably by the presence of appreciable quantities of chitin. The ligament, although superficially resembling an amphidetic structure, is opisthodetic, the extcnsion anterior to the umbones consisting of anterior outer layer only.
The mantle is characterized by an extension of the outer fold of the mantle margin which has effected equally both the inner and outer surfaces of this fold. The secretory epithelium and the modified pallial musculature, contraction of which results in the intucking and plaiting of the periostracum, is dcscribed. Simple tubular oil glands open at the mantlo margin and are responsible for the water-repellent nature of the periostracum.
The form of the mantlelshell and that of the enclosed body are discussed and compared with those of other bivalves in which elongation of the mantle/shell is achieved in a different way. It is concluded that the mantlelshell of Solemya is of little value in determining its relationships, and that the greatly elongatod ligament, the edentulous hinge and the flexible shell are all adaptations to a specialized mode of life.     

THE ADDUCTOR AND RETRACTOR MUSCLES OF THE VELIGER OF PECTEN MAXIMUS (L.) (BIVALVIA)

In Pecten maximus (L.), retractor and adductor muscles becomefunctional in the early veliger larva. The twelve-day-old veligerhas four pairs of velar retractors, three pairs of retractorsattached to the posterior body wall and an anterior adductor.The pediveliger has in addition, pedal retractor muscles anda posterior adductor. The retractors consist of striated muscle:the adductors have both smooth and striated portions. The retractorsattach near the hinge, branch to a greater or lesser extent,then attach to specific areas of the velum, posterior body walland foot. Some features of the branching and of the dispositionof points of attachment form a pattern which exhibits mirrorsymmetry about the plane between the two shell valves. Thispattern is characteristic of the species. It is deduced thatretraction and protraction of the velum result from co-ordinatedsequences of muscle contractions. ^*Present address: Forest Products Research Centre, P.O. Box1358, Boroko, Papua New Guinea. (Received 15 June 1984;     

OBSERVATIONS ON THE FAMILY CARDINIIDAE (CLASS BIVALVIA)

The composition and systematic position of the family Cardiniidaeare discussed, and the conclusion is reached that, while Cardiniaitself was an early representative of the order Heterodontida,other genera which were included in the family by Zittel, itsauthor, were unrelated forms belonging to a different order,the Naiadida. The amily Cardiniidae is, therefore, emended toinclude only Cardinia of its original members, together witha few other taxa of which Nidarica, gen.nov., is founded forthe English Liassic species Cardinia slatteri Wilson & Crick.Pseudocardinia nom. nov., proposed to replace Cardiniopsis Tornquist,1898, a homonym, is doubtfully included in the family. It ispointed out that in external morphology ome members of the Cardiniidae,including Nidarica, are remarkably like some Astartidae, andit is shown that early growth-stages of the species Cardinialaevis (Young & Bird) have been mistaken for the peciesAstarte striatosulcata Roemer. Of the other genera includedbyZittel in the Cardiniidae, the Carboniferous and Permian freshwaterbivalves are considered to belong to a distinct family, AnthracosiidaeAmalitsky, while Trigonodus is included in a new family Pachycardiidae.It is considered that the disregarded name Unionites Wissmannin Münster, 1841, should be revived to replace its juniorsubjective synonym AnoplophoraAlberti, 1864, an invalid homonym.he systematic position of this genus is discussed and its provisionalreference to the Pachycardiidae advocated. (Received 14 April 1961;     

STRUCTURE AND FORMATION OF THE BYSSUS COMPLEX IN MYTILUS (MOLLUSCA, BIVALVIA)

A review is presented of the mechanism of byssus productionin the genus Mytilus. The pedal glands which secrete the byssusmaterial are described, followed by an account of the morphology,structure and chemistry of the byssus itself. Finally, the releaseor shedding of the byssus from the pedal tissues is discussed. (Received 10 November 1981;     

THE ANATOMY OF CALLOCARDIA HUNGERFORDI (BIVALVIA: VENERIDAE) AND THE ORIGIN OF ITS SHELL CAMOUFLAGE

Callocardia hungerfordi (Veneridae: Pitarinae) lives in subtidalmuds (220 to 240m C.D.) and is covered by a dense mat of mudthat, effectively, camouflages the shell. The periostracum is two layered. The inner layer is thick andpleated, the outer thin and perforated. From the outer surfaceof the inner layer develop numerous, delicate (0.5 mm in diameter),calcified, periostracal needles. These penetrate the outer periostracum.Mucus produced from sub-epithelial glands in the inner surfaceof the mantle, slides over the cuticle-covered epithelium ofthe inner and outer surfaces of the inner fold and the innersurface of the middle mantle fold to coat the outer surfaceof the periostracum and its calcified needles. Increased productionat some times produces solidified strands of mucus which bindmud and detrital material into their fabric to create the shellcamouflage. Calcified periostracal needles have been identified in othervenerids, including some members of the Pitarinae, but how theyare secreted and how the covering they attract is producedand, thus, how the whole structure functions, has not been explained. (Received 7 December 1998; accepted 5 February 1999)     

关于晚二叠世克氏蛤类研究中的几个问题

对当前二叠-三叠纪克氏蛤类研究中存在的几个问题进行讨论,并对杨逢清等(2002)提出的关于属一级划分的原则提出质疑。通过对Claraia tumida(Patte)的再研究,确认早三叠世的克氏蛤不存在足丝凹口内端呈明显扩大的类型。经过详细的讨论和比较,无论是从形态上,或是生态上,还是从生物地理学的角度,克氏蛤和类克氏蛤在晚二叠世都应被视为两个平行发展的属。类克氏蛤在二叠纪末全部灭绝,未留下任何后裔,它与克氏蛤之间并不存在演化关系。克氏蛤的地质历程是晚二叠世早期至早三叠世晚期,发现于俄罗斯北极区新地岛晚二叠世早期的Claraia novosemelica Lobanova是克氏蛤的最早代表,它应当位于克氏蛤演化的基干部位。     

REPRODUCTIVE CYCLE AND FECUNDITY OF THE DATE MUSSEL LITHOPHAGA LITHOPHAGA (BIVALVIA: MYTILIDAE)

The reproductive cycle and fecundity of the date mussel Lithophagalithophaga, L. a well-known, ediblespecies has been examined.Sexes are separate and the mean number of eggs per each gonadis 1.894 x 10⁶ ± 1.044 x 10⁶ S.D. Reproduction firstoccurs at an age of 2⁺years and at a shell length greater than0.9 cm. Gonad activity is annual and is observed at all ages.The sex ratio for individuals up to 7 cm is 3:1 in favour ofthe males, whereas it becomes 1:1 for individuals greater than7 cm. The release of gametes by males and females occurs almostsimultaneously and begins immediately after a decline in thehighest water temperature ( 27°C), an increase in salinity(>31) and a decrease in the dissolved oxygen (6.5 ppm). Smallpercentages of mature individuals appear during the first wintermonths thus lengthening the reproductive period. This phenomenonis attributed to the temperature difference in deeper waters,the delay in gamete release by young individuals, tide, waveaction and changes in salinity. The fecundity of Lithophagalithophaga is high because its life-cycle is adversely affectedby environmental factors such as waves and tides. Fecundityincreases with shell length, more so with total wet weight andmainly with the age of the animals. Summer seems to be the suitableseason to exploit the date mussel of shell lengths > 5 cm. (Received 6 September 1993; accepted 10 March 1994)     

特提斯喜马拉雅地区早侏罗世双壳类Lithiotis生物岩礁及其扩散

藏南聂拉木地区首次发现的早侏罗世Ｌｉｔｈｉｏｔｉｓ生物岩礁,证明特提啼马拉雅地块于早侏罗世后期已开始向北运移。并且至少在早托尔斯已接近的或达到能够适应Ｌｉｔｈｉｏｔｉｏｓ繁衍的低纬度区域。     

THE OCCURRENCE OF ANOPAEA (BIVALVIA : INOCERAMIDAE) IN THE ANTARCTIC PENINSULA

The genus Anopaea represents a small but distinctive group ofinoceramid bivalves that apparently remained functionally endobyssate.The somewhat unusual morphology (for an inoceramid) probablyresults from structural modifications tofacilitate sedimentpenetration at a high angle and anchorage by an antero-ventralbyssus. Although never as common as thecontemporary genera Retroceramusand Inoceramus, Anopaea is now known from temperate bivalveassemblages in both the Northern and Southern Hemispheres. Itpersisted from the Late Jurassic (Tithonian) to the Early Cretaceous(Neocomian), and possibly even later. (Received 26 June 1980;     

BROODING AND NON-BROODING DACRYDIUM (BIVALVIA: MYTILIDAE): A REVIEW OF THE ATLANTIC SPECIES

The Atlantic species of the marine bivalve genus Dacrydium arereviewed, with particular emphasis on their hinge and protoconchcharacters. The basic groundplan of a Dacrydium comprises afunctional primary ligament, a paired series of primary teeth,and a posterior row of secondary teeth separated from the latterby a secondary ligament; this can be transformed into a singleseries either by loss of the secondary ligament and mergingprimary and secondary teeth, or by loss of secondary teeth andligament through paedomorphosis. Twelve species are recognized, of which eleven are illustrated.One abyssal species is not separable morphologically from theIndian Ocean D. speculum Poutiers, 1989 and is new to the Atlantic;four new species (D. wareni, D. dauvini, D. filiferum and D.balgimi) are described; a Caribbean form which is hardly distinctfrom the Eastern Pacific D. elegantu-lum Soot-Ryen, 1955, isdescribed as a new subspecies D. e. hendersoni. The larvae are brooded in D. hyalinum (Mon-terosato, 1875),D. viviparum Ockelmann, 1983 and D. balgimi. The brooding specieshave larger larvae (protoconch 210 to 315 µm long) thanthe non-brooding (protoconch 120 to 150 µm long), andreach a smaller adult size (1.4 to 3 mm instead of 4.5–5mm). A phylogenetic reconstruction is attempted using parsimonyanalysis of hinge and shell characters as well as the brooding/nonbrooding character. (Received 22 October 1996; accepted 28 November 1996)     

THE PALLIAL EYES OF CTENOIDES FLORIDANUS (BIVALVIA: LIMOIDEA)

The structure of the pallial eye in the Limidae has neverbeen elucidated properly, largely because they are difficultto see among the mass of surrounding mantle tentacles and becausethey are few, small, and lose their pigmentation when preserved.Possibly two eye types are present, simple cup-shaped receptorsin species of Lima, like those seen in the Arcoida, and morecomplex invaginated ones in Ctenoides. The pallial eyes (;18on both lobes) of Ctenoides floridanus are formed by invaginationof the middle mantle fold at the periostracal groove, so thatall its contained structures are derived from the outer andlight is perceived through the inner epithelia of this fold.The eye comprises a simple multicellular lens and a photoreceptiveepithelium beneath it of lightly pigmented cells and alternatingvacuolated, support cells. In some species of the Arcoidea, Limopsoidea and Pterioidea, pallialeyes occur on the outer mantle fold and thus beneath the periostracum(and shell). The pallial eyes of Ctenoides floridanus and otherpterioideans, e.g. species of the Pectinidae, occur on the middlefold and may thus have improved vision. In the Cardiodea, Tridacniidaeand Laternulidae (Anomalodesmata) pallial eyes occur on theinner folds. There is thus a loose phylogenetic trend, in which Ctenoidesis a critical link, of increasing eye sophistication correlatedwith the historical age of the clades possessing them. (Received 16 November 1999; accepted 20 January 2000)     

苏北盆地阜宁群孢粉

系统描述了湖南泥盆系的翼口蛤类标本,共5种(或亚种),其中1新种.并对国内外已发表的材料作了系统整理和厘订,指出耳部特征在此类标本研究中的重要意义.据此提出新的分类方案,建立1新亚科 Pterochaeniinae(subfam. nov.)和1新亚属 Pterochaenia (Clarkea)(subgen. nov.).为便于鉴定,还编制了检索表.     

RHAETIAN (LATE TRIASSIC) MONOTIS (BIVALVIA: PECTINOIDA) FROM THE EASTERN NORTHERN CALCAREOUS ALPS (AUSTRIA) AND THE END-NORIAN CRISIS IN PELAGIC FAUNAS

Abstract:  Species of marine bivalves of the pectinoid genus Monotis provide useful biochronologic indices for the Late Triassic (middle Norian–earliest Rhaetian). We report the succession of Monotis at Hernstein in Lower Austria where typical late Norian Monotis salinaria (Schlotheim) are overlain by strata with apparently the youngest Monotis known of demonstrable Rhaetian age: Monotis hoernesi Kittl and Monotis rhaetica sp. nov., a species closely related to M. rudis Gemmellaro. A Rhaetian (Sevatian 2) age is confirmed by the co-occurrence of Monotis with the platform conodont Misikella posthernsteini and close association with the ammonoid Paracochloceras . A review of late Norian monotid species indicates that a profound extinction event occurred in the pelagic realm at or close to the Norian/Rhaetian boundary where c. 15 monotids ( Monotis s.l . and Maorimonotis ) became extinct. The surviving Monotis are dwarfed when compared to their Norian predecessors and may represent an ecological/phylogenetic response to the crisis.     

THE FINE STRUCTURE OF THE ABDOMINAL SENSE ORGANS OF PTERIOMORPHA (MOLLUSCA, BIVALVIA)

An ultrastructural study of the abdominal sense organs (ASO)of nine species, representing all three groups Of Pteriomorpha(Mytilina, Arcina, Pteriina), is offered. In all species investigated the sensory epithelium is high (40–130µm) and possesses two predominant cell types: (a) electron-densesupporting cells with microvilli only, pigment granules, andoval distal nuclei; (b) sensory cells with round proximal nucleiand electron-lucent plasma. Their narrow processes, always bunched,reach the surface bearing long (100–300 µm) stiffcilia. Each cilium has a polarized, orientated basal foot andseveral strong roots and is surrounded by nine specialized "stereo-microvilli"forming a basal plate in connexion with the basal body. Basalcontact of the sensory cells with nervous tissue proves theirreceptive nature. Structural uniformity as well as identical innervation provideevidence for the homology of the ASO in all Pteriomorpha. Thereis no homology between sensory cells and the similar, so-called"choanocyte-like cells".