252 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.59. 



OPISTHOSIPHON (OPISTHOSIPHONA) OBTURATUM. new species. 



Plate 39, figs. 3-6. 



The shell is ovate-conic, decollated, thin but solid, umbilicus either 

 entirely closed by an affixed and adnate expansion of the peristome 

 or partially so by a less expanded peristome. The color is of a light 

 straw to dark russet, unicolored or with one dark chestnut band; 

 none are dotted. Whorls are convex with a deeply impressed suture 

 which is crenulated by the thickening of alternate lirae into hollow 

 white bulbs. The last whorl is adnate or slightly solute. The 

 sculpture consists of axial threadlike riblets which are not increased 

 in number upon the later whorls, there being about four to each 

 millimeter. Spiral sculpture is confined to about four or five low 

 cords within the umbilical region. These are not apparent in perfect 

 specimens where the umbilicus is hidden by the peristome expansion. 

 The aperture is vertical, oval, and slightly arched above. The 

 double peristome is white. The inner peritreme is not projecting 

 but slightly recurved over the outer peritreme. The latter is ex- 

 panded all around, evenly and regularly so on the outer side. On the 

 inner side it abruptly curves down to close completely or partially the 

 umbilicus and to cover a space along the penultimate whorl. Finally, 

 above the posterior angle of the aperture it again expands into a 

 concave triangular-shaped projection which is a part of and supports 

 a siphon which bends back and down to terminate in the suture just 

 back of the aperture. The surface of the expanded outer peritreme 

 is concentrically ribbed, most prominently so in the triangular pro- 

 jection above. The operculum is normal, but shows an individuality 

 in that the calcareous portion does not reach to the edge of the basal 

 horny plate. A tendency is also shown in the slight raising of the 

 edges of the lamellae to suggest the Annularia structure. 



Three subspecies are indicated : 



OPISTHOSIPHON (OPISTHOSIPHONA) OBTURATUM OBTURATUM new subspecies. 



Plate 39, figs. 3-6. 



This, the typical subspecies, is characterized by the extreme expan- 

 sion of the peristome which completely covers and seals the umbilicus 

 and becomes adnate to the adjoining whorl. The last whorl is not 

 solute. 



Type.— Cat. No. 314948, U.S.N.M., is from Paso de Lesca (or 

 Cocinas) in the Sierra de Cubitas, Camaguey Province, Cuba. It 

 measures: Length, 15 mm.; greater diameter, 10 mm.; lesser diam- 

 eter, 8.5 mm.; length of aperture within, 6 mm.; diameter of aper- 

 ture within, 4 mm. It is a female specimen. 



Taken also at the Paso de la Escalera near Ermita Vieja in the same 

 range of hills, by Torre, Henderson, and Simpson. 



