Mr. C. Spence Bate on the British Diastylidse. 463 



posterior portion of the carapace surrounding the anterior, 

 which consequently appears to be situated in the middle instead 

 of at the anterior extremity of the carapace^ and its importance 

 is so lessened in degree as to impoverish the character of the 

 appendages which it supports. Thus the eyes, instead of being 

 efficient organs, supported upon peduncles, are so reduced in 

 size and converged together as not to be distinguishable from a 

 single organ ; a circumstance which, together with the known 

 habits of the animal, induces me to believe that they are sub- 

 terranean Crustacea, living chiefly in muddy and sandy soils. 



The antennse are peculiar, sometimes one or other being rudi- 

 mentary or obsolete, but never, as far as I know, developed upon 

 the type of those of the Macroura. 



Again, the mandibles are developed upon a type so decided 

 in their character, that their form alone would be sufficient to 

 demonstrate that they do not belong to the true Macroura ; each 

 organ being furnished with a molar tubercle similar to that of 

 the Araphipoda, and not supplied with a flagellum. The maxillae 

 are developed upon the type of the Stomapoda rather than the 

 Amphipoda. This is equally correct with regard to the maxilli- 

 peds and the five succeeding pairs of appendages. 



The abdomen consists of seven segments, which, with the 

 exception of the penultimate, are generally destitute of append- 

 ages, although in the genera Bodotria and Venilia they are 

 attached to every segment, and the whole animal assumes, in each 

 of these two genera, a character more normal in its condition. 



Thus it will be seen, that the segments are developed as in 

 the adult animal ; and the appendages also, I think, possess a 

 similar signification. But should these not be admitted as suf- 

 ficient evidences of the maturity of the animals, they can further 

 be supported by the fact recorded by Mr. Goodsir, that he had 

 taken the female Cuma with '^ spawn,^^ — a circumstance that I 

 have corroborated by obtaining a C. truncatula with ova in the 

 pouch, and also a specimen of Diastylis Rathkii with larvae fully 

 developed in the same position. This latter specimen was taken 

 by G. Barlee, Esq., in the Isle of Arran. 



The female has attached to two pairs of legs four plates, ana- 

 logous to those found in the Amphipoda, which overlap each 

 other, and form a pouch in which the ova and the undeveloped 

 larvae are protected during incubation. 



The larva quits the pouch in a form resembling the parent — 

 at least so near, that, with the assistance of a most efficient 

 microscope, I have failed to distinguish any difference. Those 

 in the pouch at the same time were of two sizes, as if it contained 

 the young of separate ages, or distinct broods. 



The male in Diastylis, if not in the other genera, is capable 



