376 Mr. E. A. Smith on the Genera 



In the words of the original describers of this species, it 

 " is allied to T. ei-osa, Couth., but is easily recognized by the 

 longitudinal ribs and by its more slender form " [Mighels do 

 Adams). 



Tlie two forms are considered by Aurivillius to constitute 

 one species, and he describes and tigures a very different 

 shell under the varietal name decUvis *. Judging from the 

 tigure, 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, Repoi't Brit. Assoc. 1863, pp. 603, 

 655, name only. 



1865. Mesalia lacteola, id. Proc. Acad. Nat. Sci. Pbilad. p. 62. 



JIab. Puget Sound and Vancouver Tsl. [Cpr.). 



This species has been considered by Tryon synonymous 

 with T. reticulata, but in my opinion it is quite distinct. 

 Be.'sides being smaller and shorter, the sculpture is more 

 nodulous and the form of the aperture is different being 



Fig. 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, which 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. lig. 9 (1887). 



