Catalogue of the Heterocerous Lepidoptera collected at Singapore by Mr. A. R. Wallace, with Descriptions of New Species 183 Catalogue of the Heterocerous Lepidopterous Insects collected at Malacca by Mr. A. R. Wallace, with Descriptions of New Species 196 WALLACE, ALFRED R., Esq., and DARWIN, CHARLES Esq., F.R.S., F.L.S., & F.G.S. On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection 45 WASHINGTON, Captain. Natural-History Extracts from the Journal of Captain Denham, H.M. Surveying Vessel 'Herald,' 1857 32 WETHERELL, JOHN W., Esq. Notice of the occurrence of recent Worm Tracks in the Upper Part of the London Clay Formation near Highgate 31 INDEX 199 JOURNAL OF THE PROCEEDINGS OF THE LINNEAN SOCIETY OF LONDON. On the Importance of an Examination of the Structure of the Integument of Crustacea in the determination of doubtful Species.--Application to the genus _Galathea_, with the Description of a New Species of that Genus. By SPENCE BATE, Esq., F.L.S. [Read January 21, 1858.] Of the various genera of Decapod Crustacea none are more interesting, or more difficult of description, than those which constitute the family Galatheadae. The interest attaching to these forms arises from the intermediate position which they occupy in the natural arrangement of the class, their structure placing them between the Macrura and Brachyura; in accordance with which we find that, whilst Professor M.-Edwards classes them among the Macrura, Professor Bell, in his work on the British Crustacea, places them (more correctly, as we think) in the intermediate group of Anomura. This opinion is fully borne out both in the development of the animals and in their structure in the adult state. The early form of the larva bears, anteriorly, a resemblance to the Brachyural type, whilst the caudal appendages assimilate to those of the Macrura. The same conditions obtain in the young of Anomura. At the time of birth, the larva, like that of the Brachyura, has only the two gnathopoda developed, whilst the termination of the tail is like that of a fish, as in the Macrura. In the adult, the internal antennae possess short flagella and complementary appendages, such as exist in the order Brachyura, whilst the external antennae have the long and slender flagella proper to the Macrura. The _scale_, however, commonly appended to the external antennae in the latter order is wanting, a circumstance which exhibits a relation to the Brachyura.