No. 26.] ARTHROSTRACA OF CONNECTICUT. 61 



First five coxal plates greatly developed and presenting an 

 evenly rounded contour below. First gnathopods stouter than 

 second; propodus of both narrow. Last pereiopods with infero- 

 posterior angle of basal joint produced and acute. 



Terminal uropods with lanceolate rami which are nearly twice 

 as long as peduncle. Telson cleft beyond middle, strongly taper- 

 ing in distal half. 



This species is extensively distributed in the Arctic and north 

 Atlantic Oceans; Grand Manan; Eastport, Maine; South of 

 Block Island; near Woods Hole, Massachusetts. 



AMPELISCID^. 



Head truncate in front, no rostrum. 



Eyes simple, usually two pairs. 



First antennae without accessory flagellum. Second antenna 

 attached far behind first pair. 



Gnathopods imperfectly subchelate, carpus never shorter than 

 propodus ; second pair longer and more slender than first. First 

 and second pereiopods with very large merus ; dactyl slender and 

 elongate. 



Telson generally very deeply cleft. 



Ampelisca Kroyer. 



First coxal plate scarcely deeper than second, often concealing 

 the base of second antennae; fourth obliquely truncate below 

 posterior angle. 



Eyes four, or none, simple. 



Mandibular palp with second joint flattened and third joint 

 linear and rather short. First maxillae with outer plate trans- 

 versely truncated and palp having the terminal joint gradually 

 expanded distally and armed at the apex with several strong 

 teeth. Maxillipeds with inner plate oval; penultimate joint of 

 palp nearly club-shaped and scarcely half as long as the second 

 joint. 



Third and fourth pereiopods with very broad basal joint, 

 carpus bearing a simple row of spines within hind margin ; fifth 

 pereiopods with basal joint greatly expanded and with ventral 

 margin fringed with plumose setje; propodus foliaceous; dactyl 

 lanceolate. 



