ABT. :I0 NEW VICKSBUEG MOLLUSKS FROM MEXICO COOKE 9 



AMPULLINA VAUGHANI. new species 



Plate 2, Figures 4, 4a, 4& 



Shell small, globose, of about four whorls, spire low; aperture ellip- 

 tical, posterior half of inner lip thickened and callous; basal fasciole 

 raised, smooth, curved, sharply set off from the remainder of the 

 body whorl and from the umbilicus ; umbilicus large, open anteriorly, 

 partly covered posteriorly by the callous inner lip. Length, 5.2 mm. ; 

 breadth, 5 mm. 



This species is described from a unique specimen which may be 

 young but which appears to show the characteristics of mature 

 shells. 



Occut'rence. — Oligocene, Alazan clay, Rio Buena Vista west of 

 Alazan, Mexico. (M. 49 V.) 



Type.—Q^i. No. 352707, U.S.N.M. 



DENTALIUM OVALE, new species 



Plate 2, Figure 5 



Shell large, covered with many close-set subequal ribs, those on 

 the concave side a little finer than the others; transverse outline 

 elliptical, the shorter axis in the plane of curvature of the shell; shell 

 thick, concave side thicker than the convex. Length of fragment, 

 18 mm.; maxinuim diameter at larger end, 5.5 mm.; minimum 

 diameter, 4.8 mm. 



Occun^ence. — Oligocene, Alazan clay, Rio Buena Vista west of 

 Alazan, Mexico. (M. 49 V.) 



Type.—C2Li. No. 352708, U.S.N.M. 



DENTALIUM (DENTALIUM) ALAZANUM, new species 



Plate 2, Figures 6, 6a 



Shell moderately large, curvature slight; sculpture, near the tip, 

 of 16 longitudinal ribs, increasing in number toward the aperture 

 by intercalation, all attaining nearly equal size; entire surface cov- 

 ered with elevated transverse riblets, unequally spaced and of 

 unequal size. 



This species is known only from fragments, the largest being 16 

 mm. long and 3.5 mm. in diameter. Of living eastern American 

 species, Dentalium aluzanwn most closely resembles D. carduus Dall, 

 but its sculpture is much coarser and more irregular. I know of nc 

 comparable fossil species. 



Occurrence. — Oligocene, Alazan clay, Rio Buena Vista west of 

 Alazan, Mexico. (M. 48, 49 V.) 



Type.—Q^t. No. 352709 U.S.N.M. 



