164 PROCEEDINGS OF THE NATIONAL MUSEUM Vol.89 



present between the summit and suture. The suture is strongly con- 

 stricted. Periphery strongly rounded. Base short, narrowly, openly 

 umbilicated, well rounded, and marked by the continuations of the 

 axial ribs and by 5 strong spiral cords, which grow consecutively 

 stronger from the periphery toward the umbilicus. The junctions 

 of the axial ribs and the spiral cords become increasingly more strongly 

 scalloped from the periphery toward the umbilicus. The umbilical 

 wall is marked by the continuation of the axial ribs and by feeble spiral 

 cords. The last whorl is decidedly solute. Aperture broadly oval; 

 peristome double, the inner slightly exserted; the outer moderately 

 broadly expanded and marked by strong concentric lamellae. Oper- 

 culum typically opisthosiphonid. The siphon is at the posterior angle 

 of the aperture. It is expanded at its distal end, and it is marked by 

 concentric ridges, opening toward the suture. 



The paratypes before us were collected by Aguayo at Rejond6n 

 de Bdguanos, Holguin, Oriente. The specimen figured, U.S.N.M. 

 No. 425502, has 3.4 whorls remaining and measures: Length, 8.4 mm.; 

 greater diameter, 5.0 mm.; lesser diameter, 4.7 mm. 



OPISTHOSIPHON (SOLUTAPEX) QUESADAI Aguayo 



Plate 11, Figure 11 

 1932. Opisthosiphon quesadai Aguayo, Nautilus, vol. 45, pp. 95-96, pi. 6, fig. 5. 



Shell rather large, elongate-ovate, pale wax yellow with interrupted 

 spiral bands of brown. Nuclear whorls 2, inflated, strongly rounded, 

 microscopically granulosc, forming a mammillated apex. The early 

 postnuclear whorls are marked by rather distantly spaced axial ribs, 

 v/hich become increasingly more closely spaced as the shell increases 

 in size. On the fu^st whorl the ribs are about one-fom"th as wide as 

 the spaces that separate them, while on the last turn the ribs are only 

 a trifle narrower than the intercostal spaces. On the early whorls, 

 too, the ribs are much more lamellose than on the last, where they 

 approach rounded cords. Of the axial ribs 150 are present on the 

 last whorl. These axial ribs become expanded at the summit, where 

 they form narrow, hollow cusps. They are also expanded on the 

 middle whorls at the periphery, the two interlocking in this region. 

 On the middle whorls the axial ribs are rendered somewhat scalloped 

 by the 5 low, rounded spiral cords. On the last whorl the scalloping 

 is obsolete. In addition to the axial ribs the spaces between them 

 show the fine axial hairlines characteristic of the group. Suture 

 strongly constricted. Periphery well rounded. Base short, well 

 rounded, openly umbilicated. The umbilicus shows the continua- 

 tion of the axial sculpture and 7 strong spiral cords, of which the 

 first is the strongest and it marks the edge of the umbilicus, the rest 

 gradually becoming narrower. The junctions of these spiral cords 



