152 PROCEEDINGS OF THE NATIONAL MUSEUM Vol.89 



Shell elongate-conic, white. Nuclear whorls decollated. Post- 

 nuclear whorls inflated, well rounded, marked by slightly retractively 

 curved, lamellar, wavy, hollow axial riblets, which are developed into 

 auricles at the summit and into projections that are slightly less pro- 

 nounced at the periphery. Of these riblets 78 occur upon the first, 

 104 upon the second, and 108 upon the last of the remaining turns. 

 The spiral sculpture is obsolete on the spire, or it is at least only 

 indicated by the waviness of the axial riblets. Suture strongly con- 

 stricted. Periphery well rounded. Base short, inflated, well rounded, 

 narrowly, apparently openly umbilicated, althougli the umbihcus is 

 partly hidden by the reflected outer peristome, marked by the contin- 

 uation of the axial riblets and 5 moderately strong threads slightly 

 posterior to the umbilical angle. The tlu-ead bordering the umbilicus 

 is much stronger than the rest and causes the riblets to expand at 

 that point into strongly raised, clawlike elements; within the umbilicus 

 additional spiral cords also forming scallops are present. These, 

 however, are too much hidden to reveal their actual number. 

 Aperture almost subcircular; peristome double, the outer broadly 

 expanded, more so on the parietal and the inner lip than on the basal 

 and the outer lip, decidedly fluted at the edge and marked by concen- 

 tric lines of growth; on the parietal wall it becomes attached to the 

 preceding turn; inner peristome slightly exserted. Operculum typi- 

 cally rhytidopomid. The last whorl is adnate. The breathing siphon 

 originates at the posterior angle immediately behind the peristome 

 and is wedged into a chink formed between the preceding turn and 

 the parietal wall, but it does not extend into or plug the umbilicus. 



The specimen figured, U.S.N.M. No. 355542, is a cotype collected 

 by Poey at Managua, Potrero Almirante, Habana Province. It has 

 a little over 3 whorls remaining and measures: Length, 8.0 mm.; 

 greater diameter, 4.3 mm.; lesser diameter, 3.6 mm. 



Of this Gundlach says (Malakozool. Blatter, vol. 3, p. 126, 1856); 

 "Animal whitish, particularly on the foot. Head and neck suffused 

 with clay yellow. Antennae almost transluscent. The region 

 between the antennae, the neck and about the operculum greyish in 

 the extended animal. Animal within the shell clay-yellowish white, 

 brownish at the tip. It covers the shell almost horizontally and 

 moves with alternating wave motion." 



RHYTIDOPOMA NODULATUM (Poey) 



Shell elongate-conic, flesh colored or pale yellowish. Nuclear whorls 

 2, inflated, strongly rounded, microscopically granulose, forming a 

 very large mammillated apex, which projects conspicuously beyond 

 the outline of the rest of the spire. Postnuclear whorls inflated or at 

 least moderately rounded, marked by retractively slanting axial ribs, 

 which vary considerably in strength and elevation. The axial ribs 



