166 PROCEEDINGS OF THE NATIONAL. MUSEUM Vol.89 



It has slightly more than 4 whorls and measures: Length, 9.6 mm.; 

 greater diameter, 5.8 mm.; lesser diameter, 4.4 mm. 



OPISTHOSIPHON (SOLUTAPEX) CAROLI Aguayo 



Plate 11, Figures 9, 12 



1932. Opisthosiphon caroli Aguayo, Nautilus, vol. 45, p. 94, pi. 6, figs. 2, 3. 

 1932. Opisthosiphon rivorum Aguayo, Nautilus, vol. 45, p. 95, pi. 6, fig. 4. 



Shell elongate-ovate. Nuclear whorls 2, inflated, strongly rounded, 

 smooth, except for microscopic granules. The first 1.5 postnuclear 

 whorls are decidedly solute, strongly rounded, showing the beginning 

 of the sculpture characteristic of the later postnuclear turns. The 

 postnuclear whorls are moderately rounded and they are crossed by 

 slender, sublamellar axial ribs, of which 53 are present upon the last 

 turn in the specimen figured. These axial ribs expand at the summit, 

 where they form delicate hollow cusps, which project materially 

 above the suture. The axial ribs are marked by slender tubercles 

 having their long axis parallel with the axial sculpture ; 4 of these are 

 present between the summit and the suture. The spaces between the 

 lamellar axial ribs are crossed by exceedingly fine, microscopic, 

 closely spaced axial lirations. Suture moderately impressed. Periph- 

 ery strongly rounded. Base short, well rounded, narrowly umbili- 

 cated, and marked by the continuation of the axial ribs and by 3 

 broad low spiral cords, which render the axial ribs scalloped. The 

 umbilical wall is marked by the feeble continuation of the axial ribs 

 and by 4 strong spiral series of cusps. Aperture broadly oval; 

 peristome double, the outer broadly, flaringly expanded, a little 

 wider at the posterior angle, where it forms a slight auricle, marked 

 by a series of wavy, concentric lamellae; the inner is slightly exserted. 

 There is a puncture on the parietal wall near the posterior angle of the 

 aperture, which communicates with the short siphon; the siphon is 

 reflected backward into the suture. Operculum typically opis- 

 thosiphonid. 



The specimen figured, U.S.N.M. No. 535346, was collected by 

 Dr. Aguayo in Loma de la Caridad, Calabazas, Holguin, Oriente 

 Province. It has 3.5 whorls remaining and measures: Length, 9.3 

 mm.; greater diameter, 5.8 mm.; lesser diameter, 4.5 mm. 



An examination of topotypes of Opisthosiphon rivorum Aguayo, 

 received from Dr. Aguayo, shows that the early postnuclear whorls 

 of this shell are also solute. A comparison of all the other characters 

 in our estimation yields no data to render the two even subspecifically 

 distinct. Their identity is also proclaimed by their habitat, since 

 both species come from the same hill, separated by a distance of only 

 about 2 kilometers. 



