CRUSTACEANS THAT ARE NOT CRUSTACEOUS 245 



margin that projects and lies beneatk a corresponding 

 process of the anterior margin of the first somite of the 

 pleon, and bolts down the carapace so securely that it is 

 difficult to elevate it.' Some of the other genera show a 

 falling off from this vigorous character, for Bentheocdris 

 exuens, S pence Bate, from 2,857 fathoms in the South 

 Pacific, ' resembles many of the deep-sea forms in being 

 soft and membranous,' and both HymeTwdSra, Sars, 1876, 

 and Merdngodora, S. I. Smith, 1882, alike signify ' a mem- 

 branous skin,' the latter having for its type MeniTigodora 

 mollis from the Atlantic, and the former having been 

 instituted to receive Pasiphae glacialis, Buchholz. 



In describing Hymenodora, Sars observes : — ' With the 

 genus Pasiphae its chief agreement consists simply in the 

 two foremost pairs of feet being furnished with chelge, and 

 in all of the pairs having a natatory branch (exopodite) ; 

 but this branch is far more powerfully developed than in 

 the former genus, where it has merely the appearance of a 

 rudimentary appendix. Moreover, the two foremost pairs 

 of legs are considerably smaller, whereas the three suc- 

 ceeding pairs, which in Pasiphae are small and feeble, 

 exhibit a powerful development. From the genus Pasi- 

 phae it also differs by reason of its comparatively more 

 thickset, almost rounded form of body, the unusually thin, 

 membranaceous integumenfe, the rudimentary character 

 of the eyes, the very different structure of the oral parts, 

 and the peculiar form of the caudal appendages.' He 

 looks upon it as ' marking in some respects a kind of 

 transition to the Schizopod type,' an admission which 

 Spence Bate would appear to have overlooked, since he 

 does not refer to it in support of his own view that the 

 Schizopoda should be included among the Macrura. 



Spence Bate makes Meningodora a synonym of Hymeno- 

 dora, to which he adds several species, placing it, together 

 with Notostomus, A. Milne-Edwards, 1881, and his own 

 new genus, Tropiocaris, 1888, in a separate family Tropio- 

 caridae. But as he says that Tropiocaris in many of its parts 

 approximates so nearly to Aoanthephyra and Notostomus 

 that it can only be considered as a separate genus for the 



