528 PROCEEDINGS OF THE ACADEMY OF [Nov., 



the railroad track. Specimens taken near the cave and a short distance 

 within average smaller than those taken lower down the stream, but 

 agree with them in other characters. They measure 20 to 28 mm. 

 long. 



P. nwnachus has some resemblance to P. a. suprastriatus, but in 

 that the spiral striae are coarser and less regular, the aperture is less 

 angular above, and projects more laterally beyond the outline of the 

 cone, as in P. atratus. 



Pachycheilus vallesensis Hinkley. 



Nautilus, XXI, p. 25, pi. 5, figs. 1-3, 5-7, 10 (July, 1907). 



This species was taken in the Valles River at Valles; most abundant 

 where there is but little current. Also at the ranch of C. P. Willis. In 

 all kinds of situations. In some places the young were very numerous. 

 The largest ones were on rocks and in the bed of the river where there 

 was little or no current. The large typical form also occurred in the 

 Panuco River at Pujal, on a rock outcrop in the bed of the river. 

 This is a wide shallow stream in which there is a large amount of 

 shifting sand. Few shells were found where the stream was visited. 



Very large shells, some 37^ x 18£ mm., were taken in the Moctezuma 

 River at the ford, in the bed of the stream. 



P. vallesensis differs from the other stout species of the region by 

 its bluish, ashy or blackish-gray color, reminding one of Goniobasis 

 livescens, and by the white columellar callus. 



Pachyoheilus vallesensis attenuates n. subsp. 



The shell is livid bluish when clean, smaller and much more slender 

 than vallesensis, with a comparatively longer spire. Whorls 8 or 9, 

 the upper ones weakly striate spirally, last whorl smooth. Aperture 

 ovate, acutely angular above. Parietal callus thick and white, the 

 appressed edge often yellowish or brownish. 



Length 26, di am. 11, aperture 9 mm. 

 " 28, " 13i, " m " 



Chaimai Creek (about halfway between Valles and Pujal) and 

 Casas Viejas River, a tributary of the Valles River, coming from the 

 north of Valles, and emptying into the Valles River some miles east of 

 Mecos falls. 



These shells were at first thought to be P. suprastriatus, but they 

 differ in the striae of the young being finer and more numerous; there 

 is also a difference in the aperture and columellar callus, and the outer 

 lip is never extended beyond the line of the spire as in suprastriatus. 



In 1907 this form was included in the description of P. vallesensis 



