

The Nautilus. 



Vol. XXI. JULY, 1907. No. 3. 



DESCRIPTION OF A NEW MEXICAN PACHYCHEILTJS. 



BY ANSON A. HINKLET. 



Pachtcheilus vallesensis n. sp. PI. 5, figs. 1-10. 



Shell conic, solid, smooth ; suture impressed ; aperture widely 

 ovate, circular at the hase, obtusely angular above, purple within ; 

 whorls 7, convex ; on young and also well preserved specimens the 

 apical ones are slightly carinate or striate ; spire about half the 

 length of the shell. 



Operculum corneous, spiral, nucleus subcentral; when viewed from 

 above has a little resemblance to a small Planorbis. 



Length 32, diam. 16 mm. 



Length 33, diam. 19 mm. 



Habitat. Valles river, Valles, State of San Luis Potosi, Mexico. 



" This species resembles short forms of P. Icevissimus, from which 

 it differs by the absence of fine spiral lines, the more heavily 

 calloused columellar lip, and the darker interior. No other Pachy- 

 cheilus has been found so far north." ' 



The species is named from the river in which it is the most plenti- 

 ful mollusk. Figure 1 may be considered the type, though its size 

 is above the average. There is often a ilattening of the body whorl 

 and occasionally a constriction or shallow groove, as on some of the 

 Pleurocera. Mature specimens usually show 6 whorls ; when the 

 spire is well preserved, as in fig. 8 and fig. 9, there are 8. In young 

 specimens the aperture is angular below, sec fig. 5. In mature 



1 Note from Dr. H. A. Pilsbry. The plate illustrating this species will ap- 

 pear in the next number. 



