6 PROCEEDINGS OF THE ISTATIONAL MUSEUM vol.73 



GLYPTOTOMA RHOMBICA, new species 



Plate 1, Figures 7, la 



Shell small, outline rhombic, stout, apical angle about 57° ; nucleus 

 blunt, with two convex polished whorls, smooth except the last one- 

 fourth whorl or less, which has three faint axial riblets ; four subse- 

 quent whorls with a broad antesutural band having two strong spiral 

 threads, next, an equally broad, slightly concave band with one fine 

 thread, next, a peripheral band of the same width with two strong 

 threads; base of body whorl set with alternating coarse and fine 

 threads ; entire surface except nucleus and anterior tip cancellated by 

 close threads parallel to the growth lines; anal sinus deeper than 

 broad, coinciding with the peripheral band ; aperture broad, a little 

 more than half as long as the shell ; outer lip internally Urate, inner 

 lip with two very high columellar folds ; canal straight, flaring at the 

 tip. Length, 6 mm. ; breadth, 3.2 mm. 



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

 Alazan, Mexico. (M. 49 V.) 



Type.— Cdit. No. 352698, U.S.N.M. 



BORSONIA AGUILAE, new species 



Plate 1, Figures 8, 8a 



Apical angle about 35° ; nucleus of two or three whorls, apparently 

 smooth; posterior half of postnuclear whorls concave to a rounded 

 antesutural collar which becomes obsolete on mature whorls, smooth 

 except for faint spiral lines and growth lines; anterior half of whorls 

 with distinct spiral threads continuing to tip of body whorl, but only 

 four visible on whorls of spire ; periphery angular ; cut by short round 

 costae about as high as wide, nine costae on sixth whorl ; canal straight ; 

 aperture nearly half as long as the shell; outer lip broken, inner lip 

 carrying one strong columellar fold with a much weaker fold in front 

 of it; anal sinus semilunate, deepest part midway between the pe-' 

 riphery and the suture. Length, 12.5 mm. ; breadth, 5 mm. 



Occurrence. — Oligocene, Alazan clay, E.io Buena Vista west of 

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



Type.— C2it. No. 352699 U.S.N.M. 



ANCILLA (ANCILLINA) ALAZANA, new species 



Plate 1, Figures 9, 9a. 



Shell small, subulate ; nucleus conical, of about three convex whorls, 

 scarcely separable from the subsequent whorls; postnuclear whorls 

 barrel-shaped; suture bordered posteriorly and nearly concealed by 

 a band of enamel which extends backward from the aperture and 

 gives the earlier whorls a medially constricted appearance; aperture 



