CUBAN ANNULARIIDAE TORRE AND BARTSCH 155 



base and iii the umbilicus. Last whorl solute for about half a turn. 

 Aperture broadly ovate; peristome double, the inner moderately well 

 exserted and slightly reflected; the outer broadly, flaringly expanded, 

 somewhat wavy, marked by concentric, feeble lamellae. Operculum 

 typically rhytidopomid. The breathing siphon begins immediately 

 behind the peristome at the posterior angle of the aperture and is 

 reflected as a tapering tube into the umbilicus, which it plugs; the 

 outside of the breathing siphon is marked by strong, coarse spiral 

 rings. 



The type, U.S.N.M. No. 355604, was collected near the hghthouse 

 at the entrance to Cabanas Port, on the Tomas Barrera Expedition. 

 It has a little over 3 whorls remaining and measures: Length, 8.2 mm. ; 

 greater diameter, 4.5 mm.; lesser diameter, 3.8 mm. 



RHYTmOPOMA RUGULOSUM (Pfeiffer) 



Plate 11, Figure 8 



1839. Cyclostoma rugidosum Pfeiffer, Wieg. Archiv Naturg., vol. 1, p. 356. 

 1849. Cyclostoma rugulosum Pfeiffer, Martini-Chemnitz Conchylien Cabinet, 



ed. 2, t. 14, p. 117, figs. 9-11; t. 38, figs. 11-12. 

 1858. Ctenopoma rugulosum Pfeiffer, Monographia pneumonopomorum viven- 



tium, suppl. 1, p. 103 in part. 

 1920. Rhyiidopoma rugulosum Henderson and Bartsch, Proc. U. S. Nat. Mus., 



vol. 58, p. 69. 

 Shell elongate-conic, pale yellow. Nuclear whorls 2, moderately 

 inflated, well rounded, microscopically granulose, forming a mammil- 

 lated apex. Postnuclear whorls moderately strongly rounded, marked 

 by slender, sublamellar, rctractively slanting, axial riblets, which are 

 rendered slightly scalloped by obsolete spiral threads, of which 4 are 

 present between the summit and the periphery. The axial riblets are 

 slightly expanded at the summit. At more or less regular intervals 

 several finer axial threads occur, separating groups of the stronger 

 lamellae, which give the sculpture a somewhat interrupted pattern. 

 Of the axial ribs 51 occur on the first of the remaining turns and 96 on 

 the last. Suture strongly constricted. Periphery well rounded. 

 Base rather short, well rounded, marked by the continuation of the 

 axial ribs, which extend into the umbilicus, and by a few obsolete 

 spiral threads; edge of the umbilicus marked by a strong spiral ridge, 

 which renders the axial ribs decidedly scalloped; there is another 

 ridge, which is a little less strong, just within the umbilicus. The last 

 whorl is decidedly solute and deflected. Aperture very broadly 

 oval, almost subcircular; peristome double, the inner slightly exserted, 

 the outer broadly expanded and turned up at the junction of the inner 

 and basal lip, marked by concentric laminae, which are a little nar- 

 rower on the parietal wall than on the rest. Operculum typically 



