48 THE NAUTILUS. 



Pterides pterostoma n. sp. PI. 5, figs. 1, 2, 5, 6. 



The shell is rimate, long and slender, composed of numerous 

 slowly increasing, strongly convex whorls. Apex obtuse. Aperture 

 diagonal, obliquely oval. Peristome thin, continuous, very broadly 

 expanded, retracted and more broadly spreading at the two ends, 

 where it is somewhat spout-like. Color unknown, the specimens 

 being bleached. 



Length 2.25, diam. of last whorl above aperture .75 mm.; longest 

 axis of aperture 1.1 mm.; whorls 7 (figs. 5, 6). 



Length 2.75, diam. above aperture .8, longest axis of aperture 1.2 

 mm.; whorls 8| (figs. 1, 2). 



Eight specimens examined. There is considerable variation in 

 length and number of whorls. Figs. 5, 6 represent the type. 



Pterides rhabdus n. sp. PI. 5, figs. 3, 4. 



The shell is very slender, slowly tapering to the rather large sum- 

 mit, composed of nearly 10 very convex whorls separated by a deep 

 suture ; last whorl very convex. Aperture small, elliptical, diag- 

 onal, rounded at both ends. Peristome thin, continuous, somewhat 

 expanded, deeply sinused above, the parietal margin adnate for a 

 short distance. Length 3, diam. above aperture .75, longest axis of 

 aperture .7 mm. 



Choy River near the cave, San Luis Potosi, Mexico. 



This species is much narrower than P. pterostoma, with more 

 whorls and a smaller aperture. The outer lip may perhaps become 

 more expanded with further growth ; if so it would apparently be like 

 that of P. pterostoma. Described from a single specimen. While it 

 may possibly prove to be an extreme form of P. pterostoma, I do not 

 feel justified in uniting such unlike forms without evidence of inter- 

 gradation. 



Pterides bisinulabris n. sp. PI. 5, figs. 7, 8. 



The shell is rery slender, slowly tapering from the very obtuse 

 apex, composed of 8 smooth, strongly convex whorls, the last half of 

 the last whorl free from the preceding. Aperture diagonal, ellipti- 

 cal, the peristome continuous, free, thin, hardly expanding except at 

 the two ends, where it is retracted, slightly produced and flaring. 

 The outer margin is arched a little more than the inner. Length 

 2.5, diam. above aperture .7, longest axis of the aperture .65 mm. 



