THE NAUTILUS. 27 



smooth, the last whorl very indistinctly subangular in front of the 

 aperture, elsewhere rounded peripherally, slightly descending in 

 front. The aperture is very oblique, wider than high, about one- 

 fourth of its circumference is excised by the preceding whorl; peri- 

 stome evenly, rather narrowly reflexed throughout, slightly dilated 

 at the axial termination; parietal callus thin and transparent. 



Alt. 6, diam. 11, width of umbilicus 2 mm. 



Alt. 8.8, diam. 4.8 mm. 



Tampico, Mexico, type loc; also Valles, farther inland, in the 

 State of San Luis Potosi. 



This species is remarkable for the complete absence of teeth in the 

 aperture, in other respects having a general resemblance to Poly- 

 gyras of the texasiana group. Its generic position can be decided 

 only by examination of the soft anatomy. It may possibly be a 

 Praticolella. Six examples were taken at Tampico, one at Valles. 

 Named for the late Professor E. von Martens. 



Holospira hinkleyi n. sp. PI. Ill, figs. 3, 4. 



The shell is fusiform, widest above the middle, at the seventh 

 whorl, above which it tapers rapidly and below slowly; whitish. 

 Whorls nearly 10, the first smooth, projecting, flattened above, with 

 a central dimple, the second whorl narrower, very convex, smooth; 

 following whorls sculptured with very oblique well raised threads, 

 rather sparse on the early whorls, then more numerous, but sep- 

 arated by spaces wider than the threads. The whorls of the cone 

 are somewhat flattened, except near the lower suture where they are 

 abruptly curved, and the threads are a little enlarged. On the 

 penult and last whorls the threads become strongly arcuate ; the 

 whorls are convex, with very deep sutures. The latter part of the 

 last whorl becomes free and descends deeply. It is somewhat flat- 

 tened on the upper and outer faces, elsewhere rounded. The aper- 

 ture is transversely ovate, brown within, with a continuous, very 

 broadly expanded, flattened, thin peristome. Internally there are 

 four laminae : a strong parietal which arises in the latter part of the 

 penult and continues to where the last whorl becomes free; a shorter 

 columellar, in the median part of the last whorl; a high basal lamina 

 in the first half of the last whorl, and a thin but well-developed 

 palatal lamina, below the middle of the outer wall, in the first half 

 of the last whorl. 



