276 BTJLLETIN 181, UNITEiD STATES NATION'AIi MUSEUM 



slightly elevated; apex somewhat prominent, smooth, reddish horn 

 colored; suture channeled. Whorls 4.5, convex, the last not solute; 

 aperture almost circular, oblique; peristome continuous, straight, 

 subangulated above and shortly adnate. 



Diameter : Greater, 10 mm. ; lesser, 8.5 mm. Height, 7 mm. Di- 

 ameter of aperture, 4.5 mm. 



Type locality : Peru. 



To this Adams adds: "This species is closely allied to A. perdis- 

 tmctum, Gundl. ; but the suture is less deeply canaliculated, the 

 last whorl is not separated in front as in that species, and the raised 

 spiral lines on the whorls are reduced to one on the inner side within 

 the umbilicus." 



INCERTICYCLUS CAYENNENSIS (Shuttleworth) 



1852. Cyclostonia (CycJophorus) cayennense Shuttleworth, Berner Mitth., 1852, 



p. 299 (Diagn. n. Moll., No. 3, p. 39). 

 1854. Cj/clopJiorus cayennensis Pfeiffeb, Malak. Blatter, vol. 1, p. 86. 

 1897. AmpJiicyclotus cnyevnensis Kobei^t and Moixbndorff, Nachrb. deutschen 



malak. Ges., vol. 29, p. 139. 



We have not seen specimens referable to this species and so give 

 a translation of Shuttleworth's description : 



Shell broadly umbilicated, conoid orbicular, solid, marked by 

 oblique, undulating and anastomosing riblets, olivaceous horn colored. 

 Spire shortly conoid, somewhat obtuse; whorls 4, convex, increasing 

 gradually; the last roundly subinflated; aperture nearly vertical, 

 subcircular; spire subangulated; peristome simple, acute, continuous, 

 the upper margin produced and inbent, deeply incised at its inser- 

 tion. Columella somewhat thickened. Operculum thin, corneous, 

 closely whorled, concave externally. Greater diameter, 21 mm.; 

 lesser, 15 mm.; height, 15 mm. Aperture height, 10.5 mm.; diam- 

 eter, 9.5 mm. 



Habitat: Cayenne (Verreaux). 



Observations: To this Shuttleworth adds that he has seen three 

 specimens resembling in sculpture 6'. fOThderosuTiv Pfeiffer, texturatum 

 Sowerby, and straminemn Reeve, but the incision of the dextral mar- 

 gins of the peristome renders it very distinct. In that respect it allies 

 with G. incoTnptmn Sowebry, judging from the figure and description. 



We are greatly puzzled about the status of this species. The 

 corneous operculum would put it in the Amphicyclotinae, while the 

 description of the shell suggests aperostomine affinity. We are there- 

 fore placing it in this group of unknown relationship. 



INCERTICYCLUS DUFFIANUS (C. B. Adams) 



1845. Cyclostoma dufflanum C. B. Adams, Proc. Boston Soc. Nat. Hist, vol. 2, 



p. 11. 

 1847. Aperostoma duf/ianum Pfeiffee, Zeitschr. Mai. vol. 4, p. 104. 



