382 THE CANADIAN NATURALIST. [Oct. 



Buccinum sericatum Hancock, Ann. & Mag. Nat. Hist. [1], xviii 

 (1846), 328 ; pi. v, 6. 



Buccinum tenebrosum Hancock, Ann. & Mag. Nat. Hist. [1], xviii 

 (1846), 327; pi. v, 1, 2. (?) 



Buccinum. undulatum Hancock, Ann. & Mag. Nat. Hist. [1], xviii 

 (1846), 327 (not of Moeller). 



Tritonium {Buccinum) tenebrosum Middendorff, Malac. Rossic. (1849), 

 160; vi, 9, 11. 



Tritonium groenlandicum Moerch, in Rink's 'Groenland' Tillaeg. 

 (1857), Aftr. 84. 



Buccinum undatum Dawson, Canadian Naturalist [2], ii (1865), 88 

 (not of Linn.) 



Shell of moderate size, rather slender when full grown, thin and 

 usually of a light, fragile structure ; spire regularly tapering, 

 pointed, and produced in old specimens ; suture not deep. "Whorls 

 six to eight, not very convex, flattened near the suture, and gene- 

 rally much smoother than in any other species ; — they are neither 

 carinated nor angulated except in occasional instances by the pro- 

 minence of certain ones of the primary stride. Longitudinal folds, 

 when they exist, straight, not oblique, ten to fifteen in number, 

 extending very little below the suture. Primary spiral ridges 

 rounded, not flattened, very narrow and distant, about fourteen in 

 number on the lower whorl, often entirely obsolete, but sometimes 

 sufficiently prominent to form slight carinae, in which case they 

 do not project considerably from the proximate surface of the shell, 

 but seem to form angles rather than ridges. Secondary ridges, 

 when present, one-third as broad as the primaries, and distributed 

 upon them and upon their interspaces by about five to each ridge and 

 groove taken together. On the upper whorls in old specimens we 

 sometimes see the secondary striae regularly and closely arranged 

 with no trace of the primaries. But the characteristic primary ridges 

 as well as the secondaries, may almost always be perceived on the 

 body-whorl in adult specimens. Occasionally, in young indivi- 

 duals, the primary ridges are much more numerous than in the 

 ordinary form, and may be even broader than the interspaces. 

 Aperture two-fifths as long as the shell in the adult, (half as long- 

 in immature specimens,) and rather narrower than in B. undatum ; 

 columella rather short, smooth ; outer lip generally neither 

 thickened nor reflected, and with but a very slight sinus above 

 the middle. The outer lip is sometimes thickened in old and 

 heavier specimens, but never reflected. Colors bright but variable, 



