202 



First abdominal segment of cT so much broadened as to cover 

 in a narrow stripe the whole breadth of the last sternal 

 seo-ment Typhlocarcinops Rathbun 



12. Anterior margin of front obscurely sinuous. Cornea of eye 



extremely small, terminal. Flagellum of antenna of ordinary 

 shape, slender and naked. Merus of external maxillipeds 



not produced at antero-external angle Xenophthalmodes Richters 



Anterior margin of front distinctly bilobed. Cornea of eye 

 larger, placed ventrally at tip of eye-stalk. Flagellum of 

 antenna markedly plumed, thick. Merus of external maxil- 

 lipeds produced at antero-external angle Mertonia Laurie 



13. Eyes minute, orbits placed ventrally, not visible from above. 



Merus of external maxillipeds produced at antero-external 



aricT]g Scalopidia Stimpson 



Eyes obsolete, orbits visible in dorsal view. Merus of exter- 

 nal maxillipeds not produced at antero-external angle. . Typhlocarcinodes Alcock 



14. Eyes small, but perfect Hephthopelta Alcock 



Eyes reduced to a speck of pigment or unpigmented . . 15 



15. Antennules of normal size. Outer border of merus of external 



maxillipeds strongly convex Camatopsis Alcock 



Antennules enormously thick, the last two segments of the 

 peduncle wider than the lobes of the front. Antero-lateral 

 margins of carapace short, forming a distinct angle with 

 the subparallel and long postero-lateral ones Megaesthesius Rathbun ^). 



CeratOplax Stimpson. 



1858. CeratOplax Stimpson. Proc. Ac. Nat. Sc. Philadelphia, 1858, p. 96. 

 1886. CeratOplax Miers. Rep. "Challenger", Brachyura, p. 233. 



The genus is distinguished at once by the eyes being well developed, the eye-peduncles 

 fixed, and the antero-external angle of the merus of the external maxiUipeds conspicuously 

 produced. Otherwise it bears the greatest resemblance to TvpJilocarciniis and Typhlocarcinops. 

 As to Rhizopa, Miers thinks that it is scarcely to be separated from Ceratoplax and the recent 

 description given by Miss Rathbun appears to strengthen this presumption, but unfortunately the 

 latter author has not discussed this point. If the two genera turn out to be really identical, the 

 name Ceratoplax should disappear, occupying in Stimpson's paper a place after RJiizopa. 



The diagnostic features of Ceratoplax enumerated above prevent the including of C. 

 vtllosa and C. leptochelis, both described by Zehnter ^), into this genus, on account of the eye- 



1) K. Dansk. Vid. Selsk. Skr., 7. Raekke, M&. 5, n" 4, 1910, p. 344, based on the species M. sagedae (I.e., p. 344, textfig. 

 30 — 31 1 pl- 2, f. 5), found in very shallow water near Singapore. 



2) Rev. Suisse Zool., t. 2, 1894, p. 173—174, pi. 7, f. % and 9. 



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