Sub-Class 2. Malacostmca. Order 3. Cumacea. 213 



Order 3. Cumacea. 



The animals of this order are indeed related to those foregoing, 

 but they do not possess the same prawn-like appearance, and are 

 somewhat aberrant in many respects. The dermal skeleton is hard 

 and brittle. The carapace is so small that it only covers the 

 anterior part of the thorax, whilst the five hindmost thoracic 

 segments are bare.* The latera 1 eyes are sessile, small, 

 usually fused into one; the antenna has no exopod. Of the 

 thoracic appendages some have a swimming ramus, 

 and others have not. The first is a maxilliped, and, just as 

 in the Mysidge, it is the only one which bears an epipod, which is 

 here provided with a large lamellate gill ; the second joint of the 

 maxilliped is furnished with hooks, so that it can be fastened to 



Fig. 175. Diastylis neapoUtama, a Cumaoean. V and VIII, fifth and eighth thoracic 

 segments ; 1, 2, 7 first, second, and seventh abdominal segments ; ex exopod of a thoracic 

 foot ; He sixth abdominal appendage ; £"4, Kg fonrth and eighth thoracic appendages ; 

 eye, S carapace. — After Sars. 



its fellow. The second thoracic legs also differ from the succeeding 

 ones (as in the Mysidge), the thoracic feet are, moreover — especially 

 is this the case with the last pair — more adapted for walking than 

 those of the Mysidee and Buphausidse. The abdomen is long, thin, 

 straight, and very movable. Of the abdominal appendages, the 

 female exhibits only the last, which are backwardly directed, 

 slender, and not lamellate, and incapable of acting as a caadal fin ; 

 the males usually possess the other appendages also. The females 

 are furnished with a brood-pouch, formed by the union of lamellate 

 appendages of the thoracic feet just as in the female Mysis. The 

 young ones hatch as non-motile nauplii, like those of the last 

 mentioned order; when they leave the marsupium they are like 

 the adult, but they are still without the last pair of thoracic legs, 

 which are developed later (see Isopoda). 



The Cumacea are small animals which live on the sea-bottom at 

 sQme depth. They are met with on British coasts. 



* Among the Mysidse, too, the carapace has not coalesced with these five segments, 

 but extends over the greater part of them (the last t-n-o segments are alone 

 uncovered dorsally). 



