184 BUCCINUM. 



It might be taken for a thin and delicate form of B. undatum, 

 but is easily distinguished by the number and straightness of the 

 longitudinal plications of the spire-whorls, the more numerous 

 and sharply cut transverse ridges and the wider mouth. Occurs 

 in the pleistocene beds of Montreal, 



B. TENUE, Gray. PI. 76, fig. 327. 



Whorls convex ; with twenty-five to thirty longitudinal ribs, 

 sometimes interpolated about the middle of the body-whorl ; no 

 prominent revolving sculpture, but merely crowded minute stria;. 

 sometimes obsolete. Length, 1-75 to 2'5 inches. 



Greenland, southwards to Gulf of St. Lawrence ; Nova Zembla ; 



Lapland; Behrincfs Straits. 



This is a circumpolar species, possessing the well-known facies 

 of such shells ; its occurrence southwards in the Griilf of St. Law- 

 rence is rare and in deep water. It is a pleistocene fossil in 

 various localities from Canada northwards. The well-expressed, 

 very numerous, curved and partially duplicating ribs and the 

 almost total absence of transverse sculpture are its distinguish- 

 ing characters. B, scalar if or me, Beck, is possibly a synonym, 

 although it is also referred to Sipho Kroyeri, Moller. Besides 

 the typical form, Middendorff mentions a forma elatior, in which 

 the ribs tend towards evanescence. B. tortuosum, Reeve, is con- 

 sidered a monstrosity of this species by Stimpson, but I think it 

 more probable that it has that relation to Fusus (Sipho) Kroyeri, 

 Moller. 



B. PLECTRUM, Stimpson. 



Shell rather large, thin, elongated, whorls less convex than in 

 B. tenue, with about nineteen curved longitudinal folds, and deep 

 cut primary revolving grooves, with depressed intervening ridges. 



Length 2-23 to 2-5 inches, diam. 1/2 inches. 



Arctic Ocean, north of Behring's Straits ; 



20 to 30 fathoms. 



It may be described in brief language by saying that it has 

 nearly the form and plaits of B. tenue, with a striation of the 

 glaciale type. It evidently approaches nearest to tenue, but 

 besides the difference in the striation, the much greater regularity 

 of the longitudinal plaits will serve to distinguish it. I have 

 among a number of fossil Buccinums kindly loaned by Dr. 



