318 



THE ANATOMY OF INVERTEBRATED ANIMALS. 



The genera named, in fact, stand alone among the Crus- 

 tacea^^ in that the ophthahnic and antennulary somites are 

 complete rings, movable upon one another and the anten- 



FiG. SS.—SquiUa scabricauda.—A, the entire body, with the thorax and abdomen in 

 longitudinal and vertical section. B, the head in vertical section. I-XX, somites 

 of which the body i? compoBed. F-XX', their appeudageei, the bases of most of 

 which are alone represented, ^i, alimentary canal ; (?, stomach ; ^n, anus; C, 

 heart; 6r, branchia. N, g:ani2;lia and their commissures. B, rostrum of the cara- 

 pace ; p. the penis. Pn, endophragmal arch. The fifth thoracic appendage XI' is 

 figured separately. 



nary somite, and that their long axis is parallel with that of 

 the body, so that there is no sternal flexure. Numerous pairs 

 of hepatic creca open into the elongated alimentary canal. 

 The heart, again, is not short and broad, with at most three 

 pairs of apertures, and confined to the thoracic region, as in 

 the proper Podophthahnia ; but it is greatly elongated, mul- 

 tilocular, and extends into the abdomen. The branchias are 

 plumes attached to the abdominal members (Fig. 83, A^ hr)^ 

 and, so far as I have been able to ascertain, the carapace is, 

 in all, connected exclusively with the cephalic somites. This 



1 Unless the freedom of the anterior segment of the head in the PordflUdos, 

 referred to above, when the Copepoda were under consideration, is a parallel 

 case. 



