THE NAUTILUS. 125 



arcuate on the lower whorls. There are 43 riblets on the penult 

 whorl. In the conical part of the spire the riblets are partly 

 hollow, and broken down in places. The whorls are quite con- 

 vex, and in the lower part of the conical portion they overhang 

 a little. The last whorl is well rounded below, and carries the 

 aperture forward shortly in advance of the ventral outline of 

 the shell. Aperture is small, almost circular, a little oblique, 

 with a quite flat, reflected and continuous lip. The internal 

 axis is simple. 



Length 19.5, greatest diam. 5.3 mm.; 14 whorls remain, the 

 embryonic whorls being broken off. Aperture 4 mm. long, 

 measured outside peristome. 



Rio Conchos. Chihuahua, Mexico, not far above its confluence 

 with the Rio Grande, collected by Mr. B. H. King, 1912. 



This species is larger than any similarly sculptured Haplocion. 

 An entire specimen would have about 17 whorls, with a length 

 of slightly over 20 mm. The holotype is in coll. Bryant Walker, 

 no. 36935. 



With the preceding there were two specimens figured in pi. 4, 

 fig. 5, which appear referable to H. pasonis Dall. The riblets 

 in the last whorl are slightly closer than in a specimen of the 

 original lot of pasonis, but I can find no material difference. 

 They measure : 



Length 21.6, diameter in the middle 6.6 mm.; 11|- whorls. 



Length 21.4, diameter in the middle 6.1 mm.; llf whorls. 



NOTES ON THE BIFASCIATA GROUP OF OXYCHONA. 



BY H. A. PILSBRY. 



The genus Oxychona contains conic, acutely carinate, thin and 

 light-colored snails of eastern Brazil, evidently arboreal, distri- 

 buted from the Province of Rio to that of Bahia. Although 

 very similar in ehape to the Helicid genus Papuina, I was led 

 to place the group in the Bulimulidce, near Drymseus and 

 Zaplagius, by the characters of the teeth and embryonic shell. 



