AMPHII'dDA OF SOUTHKRN NKW ENGLAND. 



4S1 



segments, the first considerably expanded below; first and second peraeopods with dactyl slender and 

 longer than two preceding joints. Posterior peraeopods with basal joint widely expanded; ischium as 

 broad as long; merus with a posterior lobe extending to middle of carpus. Postero-lateral angle of 

 third abdominal segment broadly rounded; fourth abdominal segment in both sexes with a prominent 

 dorsal crest which increases in height posteriorly and carries a pair of short setae on its posterior mar- 



Ampelisca compressa. Vineyard Sound. '/' ; . Side plate of third abdominal segment. 



gin; terminal uropods similar in two sexes, furnished with only a few short spinules and setae; outer 

 ramus of nearly same width throughout its length; telson about two-thirds as wide as long, lol>e S 

 rather obtuse distally, but with inner angles subacute. 



Length, ti i 



Vineyard Sound; Newport; oft' Block Island; Long Island Sound. 



This is the most common species of Ampelisca in the regions around Woods Hole. It is appar- 

 ently easily obtained in large quantities, as I have examined several bottles containing thousands of 

 specimens of this species with scarcely any other amphipods. 



Ampelisca agassizi Judd. 



ByblU agassizi Judd, Proc. I", s. Nat. Mils., Vol. XVIII, 1895, p. 599, figs. '.', lOa-f, Ua-c. 



Male: Head about as long as first three segments of thorax; eyes normal; first antennae scarcely 

 half length of body; the first joint of peduncle scarcely twice as long as thick, the second nearly tw ire 

 as long as first and about three times length of third; first two or three joints of flagellum with rather 

 long setae on lower side, the remaining segments narrow, elongated, and furnished with very short 

 setae; lower sides of first two joints of peduncle furnished with tufts of very short hairs; second 

 antenna? exceeding length of body; antepenultimate and penultimate joints of peduncle with tufts of 

 short hairs above; last peduncular joint about as long as preceding one; first gnathopods with distal 

 end of coxal joint widened, and about two-thirds as long as carpus; dactyl of first and second gnatho- 

 pods about as long as two preceding joints; last perseopods with basal joint broad and produced below 

 uearly to tip. if merus, lower margin rounded; merus produced distally on posterior side as far as 

 middle of carpus; propodus fusiform, longer than carpus; postero-lateral angleof third abdominal seg- 

 ment rounded; fourth abdominal segment constricted at base, the posterior portion furnished with a 

 high rounded median dorsal crest, the following abdominal segment with a dorsal indentation; 

 terminal uropods extending beyond the others by about half the length of their rami, the rami setose 

 on both margins and not serrated; telson longer than wide, cleft nearly to base, sides convex and 

 lobes distally rounded, each furnished with a pair of short setae. 



Length, about 7 nun. 



Described from Mr. Judd's type specimens ( No. 18919) obtained from the I'. S. National -Museum. 



This species is, in some respects, intermediate between Byblis and Ampelisca, but its affinities are 



