of the North Atlantic and of North-Western Europe. 657 



greatest width central, and equal to half the length ; anterior extremity narrowly 

 rounded; the posterior somewhat apiculate. Length, 1"4 mm.; height, "8 mm. 

 It will be observed that this is a very much smaller species than the last. 



Shell of male longer and more ovate than that of the female, height rather more 

 than half the length ; both ventral and dorsal margins only gently arched, the 

 latter nearly straight in its central portion ; posterior rather obliquely truncate, as 

 in the female, but the upper spine process usually absent, the lower usually 

 present; rostrate anterior extremity even more erect than in the other sex, its 

 lower margin, as well as the sinus, fringed with rather long cilia. 



Antennae of ? (PL lvii., fig. 13), with the swimming setse much shorter than 

 in the male. Antennse of $ (figs. 2, 2 a), having, as usual, the third joint of 

 the swimming branch much longer than the second ; the swimming setse eleven. 

 The short seta, arising from the apex of the second joint, is peculiar in having 

 its external margin armed with about ten small spines ; appendicular branch 

 with two setse on the inner margin of the second joint; last joint very protu- 

 berant at the base, then suddenly and deeply incised ; this constricted portion 

 is succeeded by another j)rotuberance, after which the joint slopes away in 

 cylindrical form to the end, the cylindrical poi'tion has usually about four 

 minute tubercles on the edge, and there is a cilium near the extremity. In the 

 female the appendicular branch of the antennse has three or four small setse 

 on the basal joint; a long plumose seta on a second joint, and a distant slender 

 seta on the last. Mandible in ? (fig. 14), having the basal forked process deeply 

 cleft, and the masticating spines with only small cilia on the side, and no 

 prong. Vermiform appendage (fig. 7) with very few setse, usually six terminal 

 and four lateral. Caudal plates narrow (fig. 8), with about eleven ungues on 

 each; the five upper ungues are very small, the sixth about twice as long, the 

 seventh again very small, the eighth is considerably larger and stronger than 

 the sixth, and is followed by two terminal ungues, which are very much longer 

 and more robust than any of the preceding. 



Habitat.— Vljmouth, 1858; off Northumberland, 1862; Shetland, 1863; 

 Oban and Tobermory; Valentia, Ireland, 1870 (A. M. N,}. Cumbrae, Firth of 

 Clyde ; Loch Long (D. Robertson). 



Distribution. — Fosse de Cap Breton, S. W. France (Marquis de Folin). 



