16 PROCEEDINGS OF THE ACADEMY OF [1896. 



its outer half, the inner part bearing a rather long, low, callous 

 tooth with the summit a trifle flanged outwardly. Deep within the 

 aperture a lobe-like tooth may be seen on the columella. Parietal 

 tooth small, V-shaped, the outer ridge of the V extremely short. 



Alt. 6, greater diam. lit, lesser IO2 mm. 



The specimens serving as types were collected some years ago 

 (about 1880) by Dr. Horatio C. Wood in western Texas, either in 

 the " Great Bend " of the Rio Grande or near El Paso, exact 

 locality not noted. 



The species is somewhat allied to P. plag log lossa, having about 

 the same general contour and agreeing in the proportions of the 

 parietal lamella; but the armature of the basal lip is conspicuously 

 different, and there is a deep-seated lamella on the columella, such 

 as well developed examples of P. Mooreana show, but apparently 

 united by a low ridge with the inner end of the basal tooth. This 

 lamella corresponds to the groove within the umbilicus, and is not 

 visible in the drawings. 



P. matermontana n. sp. PI. Ill, figs. 10, 11, 12. 



Shell depressed, with low, convex spire, rounded periphery and 

 convex base ; umbilicated, the axial perforation small and deep, at 

 the last whorl rapidly enlarging to about one-fifth the diameter of 

 shell. Surface shining, faintly wrinkled by growth-lines and show- 

 ing under the lens superficial close spirals in some places; light 

 horn colored. Whorls 5i, quite convex, the inner slowly increas- 

 ing, narrow, the last decidedly wider, notably convex above, with 

 the periphery above the middle ; deeply and narrowly constricted 

 behind the lip. Suture well impressed, abruptly deflexed in front. 



Aperture quite oblique, rounded oval, the lip forming over two- 

 thirds of the circumference ; outer lip broadly expanded, flaring, 

 bearing a concave lamella with a denticle at the lower end on its 

 inner edge ; basal lip reflexed, with a compressed, slightly entering 

 tooth. Parietal callus a translucent film, bearing a V-shaped lam- 

 ella not connected with the peristome, the outer branch of the V 

 very short. 



Alt. 5"2, greater diam. 9*5, lesser 8 mm. 



Colima, Sierra Madre Mts., Mexico. 



Besides the types from above locality, there is one specimen in 

 the collection of the Academy labelled " ^Mexico " differing in size, 

 alt. 6*1, greater diam. 11 mm., and having 6 whorls. It agrees in 

 all other characters and is doubtless the same specifically. Two 

 other specimens labelled "Texas" are altogether like the types. 



