ERRATUM. Because of an unfortunate error,the index to Volume 32 as it appeared in Volume 32, 4 is incorrect. The correct Index to Volume 32 appears at the back of this issue,Volume 33, 1.

Most Hepialidae have a single-layer wing covering of hollow scales. In the South American genera Callipielus and Dalaca, however, a very characteristic ‘type-2’ bilayer wing scale covering is present. As only Callipielus and Dalaca among 28 investigated hepialid genera have this type of wing scale covering, the two genera may be considered sister taxa.     

Volume occupation, environment and accessibility in proteins. The problem of the protein surface.

The volumes occupied by atoms or groups of atoms in ribonuclease S are calculated, using a new treatment of the surface, and considering buried and exposed atoms separately. The volumes occupied by particular atom types fall within a narrow range, with standard deviations between 10% and 15% of the mean. Summation of volumes over main and side-chain groups removes inaccuracies in the single atom data, and results in even narrower distributions. Comparison of the volume spreads with those found in model glasses suggests that the remaining variation is unlikely to be much reduced by improving further either the space-subdivision method or the surface treatment. These improved volume distributions might be used as more stringent criteria against which to test trial tertiary structures.The computer program used produces additional information that could be used to investigate quantitatively the possible freedom of movement in different parts of the molecule. It also provides complementary data on environment and surface exposure.