178 PBOCEEDINGS OF THE NATIONAL, MUSEUM Vol.89 



OPISTHOSIPHON (BERMUDEZSIPHONA) OBTECTUM Torre and Henderson 



Shell elongate-ovate, rather thin, horn colored, unicolor, or banded 

 with interrupted spiral zones of brown. Nuclear whorls 2, small, 

 inflated, well rounded, microscopically granulosc. Postnuclear whorls 

 inflated, strongly rounded, and marked by slender, slightly retractively 

 curved axial ribs, which are more distantly spaced on the early turns 

 than on the later and which in some of the races become decidedly 

 reduced on the last whorl. Some of these ribs develop into slender 

 cusps at the summit at more or less regular intervals; these cusps are 

 not infrequently hollow. The intercostal spaces are marked by 

 microscopic axial threads. Suture strongly constricted. Periphery 

 inflated, strongly rounded. Base short, inflated, strongly rounded, 

 and marked by the continuation of the axial ribs and, in the exposed 

 portion of the umbilicus, by spiral threads. Aperture broadly oval, 

 almost subcircular, peristome double, the inner exserted and slightly 

 reflected on the outer lip but free from the outer, which is narrowly 

 expanded on the outer lip, a little more expanded on the inner, and 

 which forms a moderately conspicuous auricle at the posterior angle. 

 The outer peristome of the inner lip is deeply notched, and the portion 

 posterior to the notch is reflected into the umbilicus, which it plugs. 

 The outer peristome is marked by slender, concentric lamellae. The 

 operculum is typically opisthosiphonid. The siphon, situated at the 

 posterior angle of the aperture behind the peristome, connects with 

 the channel behind the parietal portion of the outer peristome and in 

 turn with the hollow axis and the decollated apex. 



The species seems to be fairly widely distributed in Santa Clara 

 Province. We are recognizing four subspecies, which the following 

 key and descriptions will help to differentiate: 



KEY TO THE SUBSPECIES OP OPISTHOSIPHON (BERMUDEZSIPHONA) OBTECTUM 



Denticles at the summit distantly spaced seibaboense 



Denticles at the summit not distantly spaced. 



Axial ribs distantly spaced obtectum 



Axial ribs not distantly spaced. 



Whorls gibbose tenuicostum 



Whorls not gibbose guayosense 



OPISTHOSIPHON (BERMUDEZSIPHONA) OBTECTUM SEIBABOENSE. new subspecies 



Plate 13, Figure 4 



This race, which was collected by Dr. Bermudez at Vereda de Her- 

 rera, Seibabo, Yaguajay, Santa Clara Province, is distinguished from 

 the other three by having all the ribs much more distantly spaced and 

 by having the denticles at the summit stronger and more distantly 

 spaced. In the type there are 30 axial ribs on the first of the remain- 

 ing whorls and 64 on the last whorl. 



