No. 26.] ARTHROSTRACA OF CONNECTICUT. 1 59 



Island Sound, July 17, 1874; off Stonington, Connecticut, 4 to 

 6 fathoms, April, 1873, rocky bottom. 



In the shape of the second gnathopods of the male I find 

 considerable variation quite similar to that described by Holmes 

 for Jassa marmorata. In a series of specimens collected by 

 Verrill off Stonington I found a number of intermediate forms 

 between the typical form with the hind margin of the propodus 

 of second gnathopod concave and the whole segment curved, to 

 the less usual form in which the propodus is oval and relatively 

 much wider than in the typical form. The series of specimens 

 was not extensive enough to allow of a generalization regarding 

 the significance of. this variation. 



COROPHIID.^. 



Body usually depressed. Abdomen small. Coxal plates 

 usually small and often not in continuity. 



Antennas of variable proportions, with or without an acces- 

 sory flagellum. 



Gnathopods variable in form and relative size. First and 

 second pereiopods usually glandular. Fifth pereiopods the 

 longest. 



First uropods biramous ; second uni- or biramous. Third 

 pair small, weakly biramous, uniramous or without rami. Tel- 

 son simple, sometimes lobate. 



Cerapus Say. 



Body slender, abdomen depressed. Head with distinct 

 rostrum. First four coxal plates very small; fifth and sixth 

 larger. 



First antennae without accessory flagellum. Flagellum of 

 first and second antennae short. 



Mouth parts normal. 



First gnathopods subchelate. Second complexly subchelate 

 and powerful in male, weak and simple in female. First and 

 second pereiopods short, glandular, front margin convex ; poste- 

 rior pereiopods short, recurved, with very short, bidentate finger. 



Second and third uropods uniramous, with ramus short and 

 uncinate. Telson short, broad, bilobed. 



