37r» Mr. E. A. Smith on the Genera 



In (lie words of the original doscrihers of this species, it 

 ** is allied to T. erosa, Couth., but is easily recognizcfl by the 

 lontritudinal ribs and by its more slender form" [Mi(jliels tfc 

 Ada vis) . 



The two forms are considered by Aurivillius to constitute 

 one species, and he describes and fit^ures a very ditTtrent 

 shell under the varietal name declivis *. Jiuli^inLr from the 

 figure, however, it certainly looks quite distinct. The whorls 

 are remarkably convex, without spiral or longitudinal costse, 

 and much higher in proportion to their width, and, in 

 addition, the peristome is entire. Without examining a speci- 

 men I must refrain from suggesting the generic position of 

 this shell. 



Tachyrhynchus lacteola (Carpenter). 



1864. Mesalia lacteola, Carpenter, Report Brit. Assoc. 1833, pp. 603, 



655, name only. 

 1805. Mesalia lacteola, id. Proc. Acad. Nat. Sci. Philad. p. 02. 



Hah. Puget Sound and Vancouver Tsl. {Gpr.). 



This species has been considered by Tryon synon3'moas 

 with T. reticulata, but in my o})inion it is quite distinct. 

 ]3esides being smaller and shorter, the sculpture is more 

 nodulous and the form of the aperture is different being 



Fie:. 3. 



produced and effuse at the base. The character of the 

 operculum, however, at once distinguishes the species. It is 

 horny, roundly ovate, but pointed above, slightly concave, 

 consists of only 4-5 whorls, wiiich increase rather rapidly, 

 are carinate at the sutures, and marked with conspicuous 

 lines of growth, and the nucleus is a little excentric. As 

 already pointed out, that of T. reticulata is circular, multi- 

 spiral, consisting of nine whorls. 



♦ Vega-Exped. Vetensk. Jakttag. vol. iv. p. 324, pi. xii. tig. 9 (1887). 



