OP CONCHOLOQY. 239 



Measurements of good specimens of eacli, are as follows: — • 

 G. plicifera. — Length 1\ inches, diameter f inch. 

 " Oregonensis. " IJ " " J " 



" huUmoides. " 1 " "I " 



The color varies from light burnt brown, through various 

 shades of yellow to light green, (the latter very rare,) and in- 

 ternally is blue, white, or very rarely purple. A single speci- 

 men is internally marked with purple lines, corresponding with 

 the external revolving strias. The substance of the shell being 

 thin, the plications cause internal grooves ; and in those speci- 

 mens which are blue within, these grooves are pure white, 

 curiously variegating them. The species is never banded. 



Localities. — Hell Gate Eiver, Washington Terr., a branch 

 of Clark's Fork of the Columbia Eiver, near the eastern bound- 

 ary of the Territory. (Dr. J. Gr. Cooper.) Columbia River 

 near its mouth. Willamette River, at Oregon City, and Eu- 

 gene City, and near its junction with the Columbia. Lake 

 George, Oregon. Nisqually River, Washington Territory. 



It will be noticed, that the extent of distribution indicated 

 above, is 900 or 1000 miles, which is far greater than usual 

 with the species of Ooniohasis. 



3. GoNioBAsis RUDENS, Reeve. — t. 24, f. 7. 



Description. — "Shell narrowly turriculated, dull olive; whorls 

 rounded, constricted at the suture, spirally ridge-striated, the 

 first strongly concentrically plicated ; aperture small, rounded. 



Habitat.—- ? 



Strongly characterized by the constricted suture, and by the 

 rib-like plications of the earlier whorls." 



In my " Synonymy of Strepomatidae," I considered this species 

 a synonym of silicula, Gould, [Shastaensis, Lea,) but a more criti- 

 cal examination convinces me that it is distinct. The whorls 

 are not so wide, are more convex, and are constantly covered 

 with prominent revolving strias, and without the broad colored 

 band so characteristic of silicula. Some of the specimens 

 from Columbia River are tinged with pink in the aperture, 

 and faintly two to three banded. But the bands are not visible 

 on the outside. The color of this species is always a light 

 burnt- brown. None of the specimens are ribbed on the body, 

 or the next whorl above it. The mouth is of curious form, 

 rather rounded-triangular, generally nearly, if not quite as 

 wide as its length, and very small in proportion to the size of 

 the shell. 



Dimensions. — Length (eroded) 4-5 inch, breadth 1-3 inch. 



Localities. — Columbia River, Oregon; and Sacramento 

 River, Cal. 



