82 



PROCEEDINGS OF SOCIETIES. 



Channel-tailed Shrimp. 

 Spec. Char. — Carapace smooth, excepting a small spine on the me- 

 dian line of gastric region, and one on each branchial ; second pair of 

 legs as long as third; sixth segment of abdomen deeply channelled 

 above ; channel continued as shallow sulcus on terminal segment ; third 

 joint of anterior pair of legs perfectly smooth ; a minute spine between 

 insertion of second pair of legs in males ; in the female spine, obsolete. 



a, tail ; b, middle plate of ditto ; c, anterior leg ; d, rostrum. 



This species is closely allied to Crangon vulgaris. The carapace is 

 large, rounded, depressed ; the rostral projection comparatively longer 

 and more acuminate ; the foot-jaws, antennae acute, and natatory plates 

 of the tail as in C. vulgaris ; the anterior pair of legs also similar, but 

 wanting the spine which adorns the arm of that species ; the spiny ar- 

 mature of the sternum differs strikingly. In C. Allmanni there is only 

 one very short spine between insertion of second pair of legs in the 

 male ; in females this is altogether wanting. In C. vulgaris I find two 

 spines present, one anterior and long, and the other posterior and 

 minute. Middle lamina of the tail is more blunted, and armed with 

 numerous teeth at the extremity, in addition to the four lateral teeth. 



The colour is bluish gray, dotted over with brown, red, and gold ; 

 length of specimens, from 1-5 to 3 inches. 



The channelled abdomen distinguishes it from C. vulgaris, fasciatus, 

 and nanus. The absence of sculpture on the abdomen, and of spinous 

 lines on the carapace, and the presence of the median spine, separate it 

 from C. spinosus, sculptus, loricatus, nanus, munitus, and hispinosus, 

 irrespective of other distinctive characters of less importance, as being 

 more or less comparative. The external characters of the shrimps would 

 enable us to separate them easily into various artificial groups, according 

 to arrangement of the spines in carapace, smoothness of abdomen, shape 

 of rostrum, &c. 



