262 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.59. 



with the inside of the shell through a pore or small opening within 

 the aperture on its posterior margin. The operculum is typical of 

 the genus. 



Type.— Cat. No. 314960, U.S.N.M., was collected by Torre at Las 

 Casimbas de las Llanadas, Sierra de Canoa, Mayajigua, Province of 

 Santa Clara, Cuba. It measures: Length, 10 mm.; greater diameter, 

 6.8 mm. ; lesser diameter, 5 mm, ; length of aperture within, 3.25 mm. ; 

 width of aperture within, 2.75 mm. 



OPISTHOSIPHON (OPISTHOSIPHON) OBTECTUM, new species. 



Plate 42, figs 2-3. 



The shell is elongate-ovate, the spire decollated, leaving three and a 

 half whorls which are convex and separated by impressed sutures; 

 the last whorl is scarcely solute. The color is a dark straw, somewhat 

 golden, the first postnepionic whorl being often slightly darker; obso- 

 lete color spots are faintly distinguishable on some specimens. The 

 sculpture consists of widely spaced, quite regularly disposed, axial 

 riblets which, in the typical subspecies, are sublamellose. Practically 

 all the riblets are expanded into hollow lamellar white bulbs at the 

 summit of the whorls, thus finely denticulating the sutures; obso- 

 lete spiral elements are so reduced as to leave slight traces in a thick- 

 ening of the axial riblets at the points of intersection. These are to 

 be observed only in the first postnuclear whorls and sometimes not 

 to be detected at all. Low, spiral cords are present on the umbilical 

 wall. The vertical aperture is slightly ovate without angle above; 

 the inner peritreme is projecting and slightly bent outward; the 

 outer peritreme is moderately expanded about evenly on all sides; 

 on the inner side it is suddenly reflected backwards and covers the 

 umbilical opening, though not widely extending over the umbilical 

 region; it then touches and is appressed to the whorl above; above 

 the aperture it is moderately expanded and projected backwards, 

 from which projection begins a recurved siphon which points down- 

 ward into the widened suture behind the aperture. The siphon com- 

 municates with the interior of the shell through a small pore just 

 within the aperture on its posterior margin. The operculum is 

 typical of the genus. 



Measurements are given under the subspecific titles. 



OPISTHOSIPHON (OPISTHOSIPON) OBTECTUM OBTECTUM, new subspecies. 



Plate 42, figs. 2-3. 



This, the typical subspecies, has the axial riblets somewhat more 

 pronounced. The outer peritreme is moio expanded and the general 

 shape of the shell is more slender than in Opisthosiphon (Opisthosiphon) 

 obtectum tenuicostatum. 



