4. E. Verrill — Catalogue of Marine Mollusca. 
563 
shells were, therefore, referred by me to that form, at first, and 
Jeffreys has, also, identified similar Gulf of St. Lawrence shells as 
N. arctica. It is possible, therefore, that JSf. arctica (Sars) is only 
another variation of the same species, with the beak shorter and 
broader than usual. 
This species, in all its forms, is nearly smooth, except for the more 
or less evident, slightly raised lines of growth, but it is usually more 
or less covered, especially when large, with a thin coating of fine 
mud or sand, easily removed. Young shells are smoother, cleaner, 
and more or less transparent. The rostrum is moderately long, not 
separated from the body of the shell by any marked sinus, the shell 
gradually narrowing into the rostrum, which tapers more or less to 
the end, and has a somewhat concave outline below ; tip more or 
less broadly truncated ; dorsal edge nearly straight, and regularly 
sloping from the hinge to the tip. Anterior-ventral border of the 
shell somewhat expanded; the anterior end evenly rounded. Um- 
bos swollen. The posterior lateral tooth, in the left valve, is a 
strong, elongated, raised ridge, variable in length, but not sharp- 
triangular as in the next species; it is continuous with the cartilage- 
pit, from which it is separated only by a small notch. 
The several forms of this species are common on muddy bottoms, 
in 50 to 192 fathoms, off the coasts of northern New England and 
Nova Scotia. We have dredged it, since 1872, off Cape Cod, off 
Cape Ann, off Casco Bay, in the Bay of Fundy, and in numerous 
localities in the Gulf of Maine and off Nova Scotia. South of 
Newport and Martha’s Vineyard, it occurred at thirty-four stations, 
in 65 to 500 fathoms, in 1880 and 1881. 
Off Chesapeake Bay, station 898, in 300 fathoniSj 1880. Oft' Dela- 
ware Bay, station 1049, in 435 fathoms, 1881. Gulf of'St. Lawrence ! 
(coll. Whiteaves). On the European coast, it is found from Spitz- 
bergen and northern Norway to the Azores. 
Neazra obesa Loven. 
Necera, obtsa Loven, Ind. Moll. Scand. Occid., p. 48, 1846. 
G. O. Sars, op. cit., p. 86, pi. 6, figs. 4 a-c. 
Verrill, Amer. Journ. Sci., v, p. 101, 1872; 1‘roc. U. S. Nat. Mus., iii, p. 398, 
1880. 
Necera pellucida Stimpson, I n vertebra ta of Grand Munau, p. 21, pi. 1, lig. 13, 1853. 
Plate XLIV, fjgurk 10, c. 
This species differs from the preceding in the somewhat broader 
and rounder form of the shell, more swollen and convex ventrally ; 
Teams. Conn. Acad., Vol,. V. 68 July, 1882. 
