HISPANIOLAN AND BAHAMAN ANNULARIIDAE 231 



these bands are arranged in both axial and spiral series. Peristome white 

 or yellowish, the outer may show the brown bands as rays. Nuclear 

 whorls 2, small, well rounded, smooth except for the last portion of the 

 last turn, which shows the beginning of the postnuclear sculpture. Post- 

 nuclear whorls moderately rounded, rather broadly shouldered at the 

 summit, and marked by rather strong, somewhat wavy, retractively 

 slanting axial riblets. Most of these riblets terminate at the summit in 

 conspicuous, sharp, strong, hollow cusps. The spiral sculpture consists 

 of slender threads as wide as or a little wider than the axial riblets; they 

 render the riblets slightly wavy. Suture strongly channeled. Periphery 

 well rounded. Base short, well rounded, openly umbilicated, and marked 

 by the continuation of the axial riblets and five or six spiral threads, 

 while within the umbilicus more spiral threads are apparent. Aperture 

 broadly oval; peristome double, the outer broadly, flaringly expanded, 

 much wider on the inner lip than on the outer, adnate to the preceding 

 turn on the parietal wall; there is a conspicuous auricle at the posterior 

 angle, which is rather irregular and is attached to the breathing siphon ; 

 inner peristome slightly exserted and slightly reflected. Operculum typi- 

 cally opisthosiphonid. 



This species is nearest related to Opisthosiphon (Opisthosiphon) turk- 

 ensis, from which it differs in not having the ribs rendered sharply cusped 

 by the spiral threads. 



It breaks up into two subspecies, which the following key and descrip- 

 tions will differentiate : 



KEY TO THE SUBSPECIES OF OPISTHOSIPHON (OPISTHOSIPHON) VAUGHANI 



Shell large, average length 9.9 mm vaughani 



Shell small, average length less than 7.7 mm occidentalis 



OPISTHOSIPHON (OPISTHOSIPHON) VAUGHANI VAUGHANI, new subspecies 



Plate 37, Figure 1 



1905. Opisthosolen hiformis bahamensis Dall, The Bahama Islands, Geogr. Soc. 

 Baltimore, p. 42, in part. 



Of this subspecies we collected thousands of specimens on various 

 parts of Mangrove Cay during the exploration of the Carnegie Institu- 

 tion's expedition to Andros Island in 1912. 



Of axial riblets, the type has 58 on the first, 60 on the second, 88 on 

 the third, and 84 on the last of the remaining turns. The slender spiral 

 threads are as wide as or a little wider than the axial riblets. They are 

 not well defined on the first turn ; on the second 8 are present and on the 

 third 12. 



The type (U.S.N.M. No. 355432) has a little over 3 whorls remain- 

 ing and measures: Length, 11.2 mm.; greater diameter, 6.3 mm.; lesser 

 diameter, 5.0 mm. 



