HISPANIOLAN AND BAHAMAN ANNULARIIDAE 



233 



OPI8TH08IPHON (OPIS'XHOSIPHON) VAUGHANI OCCIDENTALIS, new subspecies 



Plate 37, Figure 3 

 1898. Ctenopoma hahamense Pilsbry, Nautilus, vol. 12, p. 26. 



This race I collected on Gun Cay, one of the three small islands on 

 the northwestern rim of the Bahama Banks. 



There are 50 axial riblets on the first, ^2 on the second, and 82 on the 

 last of the remaining turns in the type.There are eight obsolete spiral 

 threads between the summit and the suture and five spiral threads be- 

 tween the periphery and the edge of the umbilicus, while within the 

 umbilicus 8 additional spiral threads are present in the type. 



The type (U.S.N.M. No. 355430) has a little more than 3 whorls 

 remaining and measures : Length, 8.7 mm. ; greater diameter, 4.5 mm. ; 

 lesser diameter, 3.9 mm. 



A series of 41 topotypes (U.S.N.M. No. 355430 yields the following 

 average measurements: 



This subspecies is most nearly related to Opisthosiphon (Opisthosi- 

 phon) vaughani vaughani, from which its much smaller size will readily 

 distinguish it, 



OPISTHOSIPHON (OPISTHOSIPHON) BAHAMENSIS (Shuttleworth) 



Shell elongate-conic, varying from flesh-color through horn-color to 

 pale brown ; the early whorls are frequently darker than the rest ; inter- 

 rupted spiral bands are usually present. Nuclear whorls almost 2, form- 

 ing a small apex whose whorls are well rounded and smooth except for 

 the last portion of the last turn, which shows the beginning of the post- 

 nuclear sculpture. Postnuclear whorls moderately strongly rounded, nar- 

 rowly shouldered at the summit, marked by slender, retractively curved 

 axial ribs, which vary in strength and spacing in the different races; in 

 one subspecies they are stronger than the spiral threads. These riblets 

 terminate in conspicuous cusps at the summit. The spiral sculpture in 

 two of the races is not stronger than the axial ribs. Suture strongly 

 constricted, narrowly channeled. Periphery well rounded. Base well 

 rounded, marked by the continuation of the somewhat enfeebled axial 

 ribs and more closely crowded spiral threads, which are also present on 

 the umbilical wall. Aperture broadly oval; peristome double, the outer 

 broadly expanded, a little wider on the inner and parietal wall than 

 the rest, marked by concentric lamellae forming an inconspicuous auricle 



