THE CYOLOPHORID LAiND MOI/LUSK.S OF AMERTCIA 275 



ical angulation and 6 more on the outer portion of the umbilical 

 wall. They seem to be absent in the interior. The base also has a 

 continuation of the incremental lines. Aperture circular; peristome 

 simple, sharp all around. The parietal wall is covered by a moder- 

 ately thick callus which renders the peritreme complete. The oper- 

 culum bears a low reflected calcareous spiral lamella between whose 

 turns the upturned outer edge of the basal chondroid plate is ap- 

 parent. 



U.S.N.M. No. 307404 contains the figured specimen, which was 

 collected by Cuming in Venezuela. It has 4.6 whorls and measures : 

 Height, 8.3 mm.; greater diameter, 13.2 mm.; lesser diameter, 9.8 

 mm. Height of aperture, 8 mm., diameter, 6.4. mm. 



INCERTICYCLUS, a pseudogeneric term 

 A full discussion of this proposed term will be found on p. 137. 



INCERTICYCLUS DISTINCTUS (Sowerby) 



Plate 39, Figure 11 



1843. Cyclostoma disfmcttim Soweeby, Thesaurus conehyliorum, vol. 1, p. 106, 



pi. 24, fig. 38. 

 1897. Neocyclotus (Neocyclotus) distinctus Kobelt and Mollendorff, Nachrb. 



deutschen malak. Ges., vol. 29, p. 137. 



We have not seen this species, and quote Sowerby's description 

 and copy his figure. 



"Shell orbicular, depressed, nearly flat, thin, white, with a de- 

 pressed spire, consisting of four volutions, not quite contiguous to 

 each other, rounded and spirally grooved; aperture circular, with 

 a very thin sharp-edged peritreme. 



"Bay of Montija, West Colombia; H. Cuming," collector. 



INCERTICYCLUS CONNIVENS (H. Adams) 



Plate 39, Figure 10 



1866. Aperostoma connivens H. Adams, Proc. Zool. Soc. London, 1866, p. 443, 



pi. 38, fig. 6. 

 1876. Cyclotus connivens Pfeiffeb, Monographia pneumonopomorum viventium, 



vol. 4, p. 35. 

 1897. Neocyclotus (Neocyclotus) connivens Kobei.t and Moixendobff, Nachrb. 



deutschen malak. Ges., vol. 29, p. 137. 

 1912. Neocyclotus connivens Kobelt, Martini-Chemnitz Conchylien Cabinet, vol. 



1, sect. 19, pt. 3, p. 906, pi. 140, fig. 10. 

 1923. Aperostoma connivens H. B. Baker, Occ. Pap. Mus. Zool. Univ. Michigan, 

 No. 137, p. 29 (according to Baker not an Aperostoma) . 



We have seen no specimens referable to this species and therefore 

 give a translation of Adams' description and copy his figure : 



Shell broadly umbilicated, depressed, thin, striate and unequally 

 Urate, white, covered with a yellowish brown periostracum. Spire 



