114 MESSRS. ALDER AND HANCOCK ON 



US additional facilities for understanding the species here described, and with such 

 materials at our command we hope to give a more full and accurate account of these 

 animals than has yet appeared. 



Until very lately little was known of the Nudibranchiata of the Indian Seas. Our 

 previous knowledge had been derived principally from the naturalists of the exploring 

 expeditions sent out by the French government, and especially from the splendid work 

 of MM. Quoy and Gaimard, forming the zoological portion of the ' Voyage of the 

 Astrolabe,' where many species of Nudibranchs are described and figured ; but, from 

 these naturalists not being familiar with the characters on which the distinctions in this 

 order are founded, their descriptions are often deficient in those points which are now 

 relied upon for the division of genera and species. Few of this tribe of animals have 

 been noticed by English voyagers. Mr. Arthur Adams, however, has described some 

 interesting species collected by him, in the ' Voyage of the Samarang ; ' but in all these 

 instances the animals described were procured either on the high sea or among the 

 islands of the Indian Ocean only : no exploration of the shores of continental India had 

 been undertaken. About the same time, however, as Mr. Elliot was making this valu- 

 able collection on the coast of Madras, Dr. Kelaart, stimulated by a knowledge of what 

 European naturalists were doing in this department of natural history, acquired on a 

 recent visit to England, set himself diligently to work, on his return as medical officer 

 to the garrison of Ceylon, to examine the naked Mollusca of the shores of that island. 

 The result was the discovery of more than fifty species that he considered to be new. 

 These, along with many new species of Actinia, Planaria, &c., he published in the 

 'Journal of the Royal Asiatic Society' in 1858, and subsequently in the ' Annals of 

 Natural History' for 1859. Coloured drawings of all the species had been made, 

 which are now before us : though fully equal to most of the figures of South Sea Nudi- 

 branchs previously given, these drawings have not been thought sufficiently accurate to 

 justify the expense of publication. 



Considering the proximity of the coasts of Ceylon and Madras, it was to be expected 

 that several of the species described by Kelaart would be found on the shores of the 

 adjoining continent ; we are glad to find, however, that many additional new species 

 have been discovered by Mr. Elliot, and remain now to be described. 



In comparing the Indian Nudibranchs with those of our northern seas, we are at once 

 struck with the great proportion of Dorides among the former, their great size, the 

 variety of their sculpture, and the beauty of their colours. A more remarkable fact, 

 however, is that, among the moUusks that have hitherto passed under the name of 

 Don's, there is a group of species which differ so much from that genus in a physio- 

 logical point of view as to require the establishment not only of a new genus, but even 

 of a new family for their reception. These animals have a mouth formed for suction, 

 without any trace of tongue, teeth, or jaws. They are also distinguished by the absence 



