208 PROCEEDINGS OF THE NATIONAL MUSEUM Vol.89 



OPISTHOSIPHON (CUBITASIPHONA) SOSAI. new species 



Plate 16, Figure 6 



Shell ovate-conic, white or pale yellow. Nuclear whorls 2, inflated, 

 strongly rounded, microscopically granulose. Postnuclear whorls 

 inflated, strongly rounded, and marked by retractively slanting axial 

 riblets which are distantly spaced and sublamellar on the early turns 

 and wliich are romided and rather closely approximated on the last 

 whorl. Of these riblets, 31 occur on the first of the remaining turns 

 and 162 are on the last. At irregular intervals these riblets are 

 gathered into hollow cusps at the summit. Suture strongly con- 

 stricted. Periphery decidedly inflated, strongly rounded. Base 

 short, inflated, strongly rounded, marked by the continuation of the 

 axial ribs. Within the umbilicus and on its outer edge a series of 

 slender spiral cords are present that render the riblets feebly scalloped 

 at their junction. Aperture broadly oval; peristome double, the 

 inner exserted and sUghtly reflected; the outer narrow on the outer 

 and basal lip, expanded into a conspicuous auricle at the posterior 

 angle, and broadly expanded on the inner lip, on the middle of wliich 

 it shows a conspicuous fold. Posterior to tliis fold it is reflected 

 partly over the umbilicus. The entire outer peristome is marked by 

 numerous, concentric lamellae. Operculum typically opisthosiphonid. 

 Siphon at the posterior angle of the aperture directed backward into 

 the suture. 



The type, U.S.N.M. No. 535476, comes from Loma Caracuna, 

 Finca Marchena, Siboney, Camagiiey Province. It has 3.8 whorls 

 remaining and measures: Length, 11.2 mm.; greater diameter, 8.3 

 mm.; lesser diameter, 6.3 mm. 



OPISTHOSIPHON (CUBITASIPHONA) LITORALE, new species 



Plate 16, Figure 7 



Shell broadly ovate, pale brown with a peripheral chestnut-brown 

 band. Nuclear whorls decollated in aU our specimens. Postnuclear 

 whorls inflated, strongly rounded, marked on the first of the remaining 

 turns by very slender, distantly spaced axial riblets, which become 

 finer and more closely approximated as the whorls increase in number. 

 They are exceedingly fine on the last turn. At distant intervals 

 these riblets are gathered into inconspicuous cusps at the summit. 

 In the type 53 of the axial ribs are present on the first turn and 192 

 on the last. Suture strongly constricted. Periphery inflated, 

 very strongly rounded. Base short, very broadly, openly umbili- 

 cated, marked by the continuation of the axial ribs and by a series of 

 closely approximated, low, broad, rounded cords in the umbilicus 

 and on the outer umbilical wall. Aperture broadly oval; peristome 



