264 



The "Siboo-a^' specimen affords the first record of this genus from the Indo-Malayan 

 Archipelago. 



Dimensions in mm. 



Length of carapace 3.95 



Breadth of carapace 4.2 



Dactyli of 3d pair of walking legs . 0.85 



Dactyli of 4th pair of walking legs . 1.2 



Subfam. Pinnotherelinae. 



In the typical representatives (of the genera Pinnothcrclia H. Milne-Edwards and Pinnixa 

 White) the ischium of the external maxillipeds, though distinct, is much smaller than the merus, 

 and forms together, with this merus a broad plate, the longitudinal axis of which, like in the 

 Pmnotherinae, though not quite transverse, is directed obliquely to the median axis of the 

 animal; the palp is very large and fills to a great extent the gap between the maxillipeds, 

 its joints are produced beyond each other and the propodus projects largely beyond the basal 

 part of the broad dactylus ^). The carapace (in Pimiixa at least) is much broader than long, 

 and the last pair of legs is often reduced in size. 



Closely related to Pinnixa is Tetrias Rathbun (Alcock even considers the latter merely 

 a subgenus of the former), but the external maxillipeds are placed more longitudinally, the 

 segments of their palps are much broadened and flattened, and the propodus is truncate, not 

 produced beyond the insertion of the dactylus. 



A fourth genus, Pseudopinnixa, Ortmann, also certainly belongs to the present group, 

 but the carapace is subcircular (at least in the type species) and the segments of the palp of 

 the external maxillipeds are placed end to end, the dactylus being very much elongate and 

 cylindrical. 



Alcock ~), though in two cases doubtful about the matter, includes still the following genera : 



Malacosouia de Man. I have examined the type specimen of the only species known and can 



assert that it truly belongs to the Asthenognathinae. 

 Opisthop2is Rathbun. This genus is very little known. Miss Rathbun herself ranges it among the 



Asthenognathinae. The external maxillipeds seem to resemble those of the. next genus. 

 Tritodynamia Ortmann. Notwithstanding some unmistakable resemblances to the Pitmotherelinae 



it seems preferable to refer this genus also to the Asthetiognathinae. 



In recent years Miss Rathbun founded a genus JMortensenella^ referred by her to the 

 Pinnotherelinae. If we adhere, however, to the typical genera of this group, the genera Mor- 

 tensenella does not belong to it, and provisionally I prefer to range it among the Asthenognathinae., 



1) This arrangement agrees with what is found in Piniuixadis., a genus of the preceding subfamily, which, however, is connected 

 l>y gradual transitions to Piiinotheycs. 



2) Journ. As. Soc. Bengal, v. 69, prt 2, 1900, p. 294. 



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