; 



An Account of the Deep-sea Brachyura collected by the Royal Indian Marine Survey 

 Ship " Investigator'"— By A. Alcock, M.B., C.M.Z.S., F.G.S., Superinten- 

 dent of the Indian Museum and Professor of Zoology in the Medical College 

 of Calcutta : formerly Surgeon- Naturalist to the Indian Marine Sxirvey. 



With two exceptions — namely, a Homola that is very possibly identical with 

 the deep-sea Homola orientalis of Henderson and a singular species of Bynomene 

 — the Brachyura here described came from depths over 100 fathoms. 



The species number 53, and belong to 38 genera, and they have been 

 collected by the 'Investigator' during the last fourteen years (1885-1898). 

 Specimens of all, including the types of new species, are in the Indian Museum. 



Of these 53 species only the following five are known from other seas : — 

 EtJmsina gracilipes Miers, Cyrtomaia Suhmi Miers, Platymaia Wyville-Thomsoni 

 Miers, Oxypleurodon Stimpsoni Miers, Scyramathia pulchra Miers. These five 

 are " Challenger " species from the seas of the East Indian Archipelago, but 

 Ethusina grarilipes has also, according to Faxon, been taken off the Pacific coast 

 of the Panama region. 



To those who expect a faunal list to furnish forth some theory of geogra- 

 phical distribution, our list will appear disappointing. 



If, however, we regard genera and not species, the hst discloses some 

 suggestive affinities between the Brachyuran fauna of these Seas and of certain 

 parts of the Atlantic area. These affinities may, of course, be taken as merely 

 confirmatory of current views as to the unity of the Deep-sea Fauna ; but, 

 seeing that the Brachyura are not generally considered to belong to the true 

 deep-sea (abyssal) fauna, I think it equally probable that they may afford 

 evidence of a former open connexion between the seas in question. 



In an Account of the Investigator Deep-sea Madreporaria (pp. 2-10) I have 

 discussed this matter at some length, so that here I need speak only of the 

 supplementary evidence that the deep-sea Brachyura appear to furnish of this 

 connexion. 



Of the 38 genera that are at present known to compose the Brachyuran 

 fauna of the Indian depths the following 21 are also known to occur in other 

 seas : — Homola, Dynomene, Calappa, Mursia, Bandallia, Ethusa, Ethisina, Lyrei- 

 dus, Echinoplax, Cyrtomaia, Platymaia, Sphenocarcinus, Oxypleurodon, Scyramathia, 

 Maia, Trichopeltarium, Trachycarcinus, Goniosoma, Pilumnoplax, Carcinoplax, 

 Pinnoteres. 



