CRUSTACEA. 291 



or lobe on its inner margin, which fits into a cavity between two 

 smaller teeth on the inner margin of the lower finger. These cha- 

 racters are, however, less marked in specimens in which the second 

 lcps are less developed, and there are one or two examples in which 

 the chelae scarcely differ in form and proportions from Dana's figure ; 

 hence I have not ventured to regard the species as distinct. 



A specimen, dried and very imperfect, which probably belongs to 

 this species, is in the British-Museum collection from Keppel Island, 

 Port Curtis, obtained within the shell of a live Pinna (•/. Macgilli- 

 vray, H.M.S. 'Rattlesnake'), others from the collection of H.M.S. 

 'Herald,' from the interior of Tridaena (without indication of 

 locality), and others from Matuka and Ngau {H.M.S. 'Herah/'). 

 In all the specimens from the ' Herald ' collection the second pair 

 of chelipedes are less developed, as in Dana's figure of this species, 

 which was based on a specimen from Tutuila, in the Samoan or 

 Navigator group (Crust. U.S. Expl. Exp. xiii. p. 571, pi. xxxvii. 

 fig. 1, 1852). 



It appears very doubtful whether the P. maculata, Stimpson*, 

 from Tridacnce obtained at Bonin, can be regarded as distinct from 

 P. tridaoKP, from which it is only distinguished by Stimpson by 

 its elongated form and slenderer rostrum ; the rostrum is, how- 

 ever, described as reaching only to the penultimate joint of the 

 antennulary peduncles (and hence shorter than is usual in P. tri- 

 daena) and truncated at apex. 



The genus Conchodj/tes, established for this species by Dr. Peters, 

 can, I think, scarcely be regarded as generically distinct from 

 Pontonia ; but the name may perhaps be conveniently retained as a 

 subgeneric designation for P. tridaena'. and the allied species. Dr. 

 Hilgendorf, who had the opportunity of examining Dr. Peters's 

 type, distinguishes it from Pontonia merely by the shorter antennal 

 flagellum t ; but the flagellum in P. macrophthahna (which Dr. Peters 

 himself supposes to belong to Conchoch/tes) is represented as being 

 much longer. (See M.-Edwards, Atlas in Cuvier's ' Regne Animal,' 

 Crustaces, pi. lii. fig. 3.) 



12. Harpilius inermis. (Plate XXXII. fig. B.) 



Body not compressed, smooth, and dorsally rounded, and without 

 spines either on the carapace or postabdomen. Rostrum spiniform, 

 rounded and smooth above, longer than the eye-peduncles, rather 

 broad at base, appearing acute at apex in a dorsal view, without 

 spinules or teeth on its upper or lower margins ; it is laterally 

 somewhat compressed, and in a lateral view its apex is rounded. 

 The terminal postabdominal segment is rounded above, but narrows 

 considerably towards its distal end, which bears several seta? ; the 

 lateral margins are unarmed. The eye-peduncles project laterally 

 and are of moderate size ; the antennulary peduncles project slightly 



* Proc. Acad. Nat. Sci. Philad. p. 38 (1860). 

 t Sitzungsb. der Akad. Wissenech. Berlin, p. 835 (1878). 



TJ 2 



