153 



a commensalistic mode of living with Lamellibranchs, in worm-tubes, corals etc. is either proved 

 or rendered most likely. 



The monographer's task is greatly impaired by a large number of species, and even of 

 not a few genera, being very incompletely known and especially by the scarcity of good figures. 

 Alcock indeed has given a most useful synopsis of British Indian species; he distinguishes the 

 following subfamilies: Pseudorhombilinae, Goneplacinae, Prionoplacinae, Rhizopinae and Hexa- 

 podinae. Miss Rathbun ') has afterwards proposed a new subfamily, Typhlocarcinopsinae, which 

 for reasons explained further on I have not maintained. 



The discrimination of the subfamilies has been given by Alcock. 



Subfam. Pseudorhombilinae. 



1852. Carcinoplacinae H. Milne-Edwards. Ann. Sc. Nat. (3), t. 18, p. 164. 



1886. Carcinoplacinae Miers. Rep. "Challenger", Brachyura, p. 223. 



1900. Pseudorhombilinae Alcock. Journ. As. Soc. Bengal, v. 69, prt 2, p. 286, 292. 



Alcock enumerates, though sometimes with a query, fifteen genera of the subfamily, 

 removing at the same time Geryoji Kroyer and Camptoplax Miers, that are referred to the 

 Xanthidae. Of these fifteen genera Brachygrapsus Kingsley is almost certainly identical with 

 Litocheira Kinahan, Camptandriuin Stimpson has now turned out to be one of the Ocypodidae 

 (see p. 68 of the first part of the present paper), Cryptocoeloiiia Miers is very little known and 

 has been doubtfully referred by Miers himself to the Rhizopinae, Heteroplax Stimpson is most 

 likely synonymous with Eticrate de Haan, and Platypihtvinns Wood-Mason seems to belong 

 to the Xanthidae. 



So there remain ten genera, of which two, viz. Frevillea A. Milne-Edwards-) (not Frey- 

 villea as Alcock spells it) with three species, and Bathyplax A. Milne-Edwards 3) with a single 

 one*), are Atlantic and live on the western side of this ocean. Miss Rathbun afterwards added 

 two new genera, Te trap lax'"), with one species, from the West Indies, and Trizo care inns''), 

 likewise with one species, from the Gulf of California. All these American genera, except perhaps 

 the last, are most incompletely known and, except for Bathyplax and Trizocarcinus, have 

 never been figured. 



This subfamily, like the Prionoplacinae, has the utmost affinity with such Xanthoid forms 

 like Encratodes A. Milne-Edwards and indeed it is nearly impossible to trace a distinct boundary; 

 on the other hand the genus Catoptrus A. Milne-Edwards is perhaps better to be referred to 

 the Portunidae. 



I have here, following Alcock, retained the name of the subfamily, but the genus 



1) K. Dansk. Vid. Selsk. Skr., 7. Raekke, Afd. 5, n» 4, 1910, p. 345. 



2) BuU. Mus. comp. ZooL Haivavd CoU., v. 8, 18S0, p. 15. 



3) L. c, p. 16. 



4) Miers (Rep. "Challenger", Brachyura, 1886, p. 230, pi. 20, f. 3) describes a subspecies. 



5) Bull. U.S. Fish Comm. for 1900, v. 2, 1901, p. 9. The type is Frevillea qmidrh/enUth, Rathbun, Bull. Lab. Nat. Hist. State 

 Un. Iowa, V. 4, 1898, p. 287, p. 8, f. I. 



6) Proc. U.S. Nat. Mus., v. 47, 1914, p- "7, textfig. I, pi. I. The type is Carciiwplax dentata Rathbun, Proc. U.S. Nat. Mus., 



V. 16, 1893, p. 243. 



5 



