J76 CRUSTACEA. AMPHIPODA. 



the first four feet or exterior feet-jaws in the form of compres- 

 sed arms, dentated below ; the two anterior smaller and an- 

 nexed to the head ; fifth pair of feet largest, didactyle ; six 

 vesicular sacs in three pairs at the internal base of the last 

 six feet ; head very large, cordiform, vertical ; body very soft, 

 narrow and long; tail terminated by six elongated styles, 

 forked at the end, and four or six swimming feet on the third, 

 fourth, and fifth rings. 



P. sedentaria, Lat. Six caudal swimming feet ; body semitranspa- 

 rent, silvery, and dotted with red. 1 inch long. Inhabits Eu- 

 ropean seas. B. Lat. Gen. i. pi. 2, fig. 2. 



FAMILY II. UROPTERA. 



Lateral appendages at the posterior extremity of the body in 

 the form of leaflets, and serving as fins. 



Gen. 15. HYPERIA, Lat. 



Four setaceous antennae ; the ten proper feet terminated by a 

 simple and pointed joint ; head small, round, not prolonged 

 into a rostrum ; body conical, terminated by two triangular 

 elongated and horizontal laminae. 



H. Suerii, Lat.Desm. Crust. 258. 



Gen. 16. PHROSINE, Risso. 



The two superior antennae large and spoon-shaped ; the two in- 

 ferior setaceous and very small ; ten proper feet monodactyle, 

 the fourth pair largest, with the first joint broad and oval, 

 the two following triangular, and the last long, sharp, and 

 falciform ; body oblong ; head prolonged into a rostrum ; tail 

 of five quadrangular segments, terminated by two oblong ci- 

 liated laminae. 



P. semilunata, Risso. Body oblong, yellowish anteriorly, red pos- 

 teriorly ; head with two small horns forming a crescent ; eyes 

 small. 7 or 8 lines long. Coasts of Nice. Desm. Crust. 259. 



FAMILY III. DECEMPEDES. 

 With only ten feet. 



Gen. 17. TYPHIS, Risso. 



Two very small antennae and eyes ; head thick, short, and as 

 if truncated ; body ovoid, convex above, arched below, of se- 

 ven segments, with lateral appendages ; abdomen of five seg- 

 ments, terminated by four rounded and ciliated scales ; feet, 

 the first four didactyle ; the last four laminar, and terminat- 

 ed by a hook. 



T. ovoides, Risso. Body smooth, shining yellow, with reddish dots. 

 Inhabits coasts of Nice, in sandy bottoms, and rolls itself up into 

 a ball when alarmed. Risso, Crust. 122. 



