38 University of Michigan 



wrinkled; next whorl with microscopic growth-wrinkles and 

 mimerous, low growth-ridges; spiral sculpture and definite 

 growth riblets begin on 3rd whorl ; all apical whorls convexly 

 rounded and with well-impressed sutures. Umbilicus: small, 

 tubular; hidden by last whorl. Aperture: broadly obovate, 

 almost circular, and with long axis at about 45° to that of the 

 shell; internally light -colored with prominent, spiral bands. 

 Peristome : duplex ; outer portion abruptly deflected ; parietal 

 angle with prominent, lanceolate auriculation, which is eon- 

 cave externally and is slightly twisted backwards at its inner 

 edge; lower palatal, basal and lower columellar walls with 

 (almost invariably) 5 elliptical reflections, separated by 6 

 deep sinuses which correspond to the positions of the more 

 prominent color bands; upper columellar region broadly re- 

 flected; parietal wall narrowly reflected; inner portion of 

 peristome continuous but without internal callus. 



Operculum (fig. xi-42) : 4 to 414 whorls; almost circular; 

 nucleus subcentral but slightly nearer basal angle; chondroid 

 plate heavy, almost flat but with rim of each whorl slightly 

 raised ; calcareous portion represented only by irregular punc- 

 tations. 



Radula (fig. ix-26) : C/3; Ll/6-8 + 1/4; M/28-32. Rha- 

 chidia central: cowl-shaped, with large cusp curved over the 

 anterior end and a minor one on each side ; thickened portion 

 of base ovoid, but thinner wings make the entire tooth a 

 truncated isosceles triangle. Inner lateral: shape similar to 

 central but asjTnmetrical, with the thickened, inner edge 

 longer than the thin, outer one ; the three principal cusps are 

 similar in arrangement to those of the central, but the middle 

 one almost alwaj^s bears two serrations on either side near its 

 base; on a few teeth only one of these last could be seen on 

 the inner side while in a few others three were counted on the 

 outer side (the refraction of the edge of the main cusp makes 

 the definition of these small points very poor) . Outer lateral : 

 with a curved, rectangular base which bears 4 stout, aculeate 

 cusps at its outer end. All of the three inner teeth are thick- 

 ened transversely just below the cusped tips ; when the second 



