238 AMERICAN JOURNAL 



2. GoNioBAsis PLiciFEEA, Lea. — t. 24, f. 3, 4, 5, 6. 



Description. — "Shell acutely turrited, rather thick, nearly 

 black; spire full of folds; apex truncate; whorls somewhat 

 convex, the last being smooth above and striate below ; aper- 

 ture white. 



Sahitat. — "Wahlamat, near its junction with the Columbia 

 Eiver. Prof. Nuttall. 



Dimensions. — Diameter '4 inch, length 1"1 inches. 



JRemarks. — Among the fine shells brought by Prof. Nuttall 

 from beyond the Kocky Mountains, was this single species of 

 Melania. It is remarkable for its numerous folds, or ribs, 

 which fill the superior whorls. The inferior whorl is entirely 

 without these ribs, but the inferior portion is furnished with 

 transverse striae. I am indebted to Prof. Nuttall for many 

 specimens of this shell, all of which are more or less truncate 

 at the apex. The most perfect one, which is small, has nine 

 whorls." 



The shell described by Mr. Lea is only one of several varie- 

 ties (?) of form assumed by this species. It is characterized 

 by flat whorls, slight suture, and particularly by the body 

 whorl being free from ribs, and slightly angulated at the 

 periphery. (Fig. 3.) Fig. 384 of Eeeve's Monograph of Mela- 

 nia represents this variety. 



Dr. Gould (Expl. Exped. Shells, p. 143,) remarks that 

 "This shell seems to be subject to great variety, or else there 

 are several allied species." 



After an examination of a large number of specimens, we 

 have selected two other forms, which we propose to designate 

 as varieties^ with names, for the present. All the specimens 

 examined appear to be included in these three forms. 



Var. Oregonensis. — Shell very long, sub-cylindrical, whorls 

 very convex, plications slight on the body whorl, which is not 

 angulate at the periphery. The whole surface is thickly cov- 

 ered with revolving striae. (Fig. 4.) 



Var. BULIMOIDES. — Shell short, inflated; whorls very con- 

 vex, with plications on all of them; either covered with close re- 

 volving striae, (Fig. 5,) or the striae obsolete, (Fig. 6.) Fig. 164, 

 Gould's Expl. Exped. Shells, represents this variety. 



Of these forms, Oregonenis appears to be by far the most 

 common, embracing near nine-tenths of the specimens before 

 me, the balance being about equally divided between the 

 other two. 



