HISPANIOLAN AND BAHAMAN ANNULARIIDAE 241 



whorls remaining and measures: Length, lo mm.; greater diameter, 

 5 mm. ; lesser diameter, 4.2 mm. 



This species differs from Opisthosiphon (Leptopisthosiphon) coloni 

 in having intercalated axial threads between the heavier ribs. It is also 

 geographically separated from O. (L.) coloni, having been collected back 

 of Victoria Hill Settlement, San Salvador. 



OPISTHOSIPHON (LEPTOPISTHOSIPHON) COLONI, new species 



Shell elongate-conic, flesh-colored, pale horn-colored, or pale brown, 

 unicolor or interruptedly spirally banded; the peristome is flesh-colored 

 or yellowish white. Nuclear whorls a little more than 2, small, well 

 rounded, smooth except for the last portion of the last turn, which 

 shows the beginning of the axial sculpture. Postnuclear whorls moder- 

 ately rounded, narrowly shouldered at the summit, marked by slender, 

 retractively slanting axial riblets, some of which become expanded at 

 the summit to form slender hollow cusps. Suture almost channeled. Pe- 

 riphery well rounded. Base rather long, well rounded, marked by the 

 continuation of the axial ribs; the umbilicus is usually closed by the 

 reflection of the inner peristome. Aperture broadly oval; peristome 

 double, the outer thickened, reflected and expanded, appressed to the 

 preceding turn on the parietal wall and reflected over the umbiUcus 

 which it may partly or completely close. Operculum paucispiral with the 

 nucleus submarginal. The whorls are marked by retractively slanting, 

 slender lamellae which are fused on their inner and outer border, but 

 do not extend to the outer edge of the basal chondroid plate, leaving a 

 narrow band of this showing between the turns, i.e., typically opisthosi- 

 phonid. 



This species is confined to the Island of San Salvador (Watling 

 Island), where it breaks up into several subspecies as follows: 



KEY TO THE SUBSPECIES OF OPISTHOSIPHON (LEPTOPISTHOSIPHON) 



COLONI 



Umbilicus closed by reflected outer peristome. 



Axial ribs on last whorl conspicuous henryi 



Axial ribs on last whorl obsolete colom 



Umbilicus not closed by reflected outer peristome ferdinandi 



OPISTHOSIPHON (LEPTOPISTHOSIPHON) COLONI HENBYI, new subspecies 



Plate 37, Figure 6 



This subspecies, like typical Opisthosiphon (Leptopisthosiphon) coloni 

 coloni, has the umbilicus closed by the reflection of the outer peristome, 

 but it has the axial ribs much more strongly developed than in the typi- 

 cal race, and these are not obsolete on the last whorl. 



The type (U.S.N.M. No. 355427) is a complete specimen having 7.0 

 whorls and measures: Length, 12.6 mm.; greater diameter, 4.7 mm.; 



