THE NAUTILUS. 



Vox,. XXII. JANUARY, 19O8. No. 9. 



POMATIOPSIS ROBUSTA N. SP. 



BY BRYANT WALKER. 



Shell ovate-conic, perforate, smooth and shining, lines of growth 

 subobsolete; light greenish-yellow becoming lighter towards the 

 apex ; spire elevated, apex blunt, the initial whorl being perceptibly 

 flattened. Whorls 5^, convex, with a well impressed 

 suture, body whorl large and inflated. Aperture 

 ovate, narrow above and well rounded below, between 

 one-third and one-half of the length of the shell ; 

 peritreme continuous and adnate to the parietal wall 

 above the perforation ; lip sharp. 



Alt. fi, diam. 3^ mm. 



Jackson Lake, Wyoming. 



Type in the collection of A. A. Hinkley, Du Bois, 111. 



Although only a single specimen of this species was found, it is so 

 obviously distinct from any of the known species of the genus, that 

 I do not hesitate to describe it. 



It is a much stouter shell than P. hinkleyi and differs from both 

 that and californica in the less convex whorls and less impressed 

 suture. In these particulars it resembles more P. lapidaria, but 

 differs from thai entirely in shape. The narrow perforation and 

 sharp lip as well as the general contour easily separate it from P. 

 cincinnatiensis . 



