HISPANIOLAN AND BAHAMAN ANNULARIIDAE 97 



U.S.N.M. No. 536868 contains 5 specimens from Cayo de Tamaso, 

 Santa Barbara de Samana. 



U.S.N.M. No. 536869 contains 2 specimens from Cayo Paloma, 

 Samana Bay. 



COLONINA, new genus 



Shell moderately large, elongate-ovate, with closely spaced axial riblets, 

 which are rendered vertebrated by the spiral sculpture. The axial ribs are 

 gathered into tufts at the summit and project above this as conspicuous 

 denticles. Aperture oval; peristome double, the outer expanded on the 

 inner lip, slightly so on the outer, or this may be fused with the inner 

 peristome to form a sharp edge. The operculum bears a slightly raised 

 lamella on the inner edge of the whorls, from which strongly elevated, 

 retractively slanting, slender lamellae radiate outwardly, fusing at their 

 outer edge into a solid ridge. The calcification of the operculum does not 

 extend to the outer edge of the chondroid basal plate, but leaves a small 

 space showing between the turns. 



Type species: Colonina fortunensis, new species, from the Bahamas 

 (for description see page 245). 



KEY TO THE HISPANIOLAN SPECIES OF COLONINA 



Last whorl solute. 



Summit of the whorls strongly denticulated tortuensis 



Summit of the whorls not strongly denticulated manielensis 



Last whorl not solute. 



Axial riblets fused into a solid band at summit molensis 



Axial riblets not fused into a solid band at summit. 



Whorls decidedly inflated moustiquensis 



Whorls not decidedly inflated haitensis 



COLONINA TORTUENSIS, new species 



Plate 15, Figure 3 



Shell elongate-conic, white. Nuclear whorls inflated, strongly rounded, 

 microscopically granulose. Postnuclear whorls strongly rounded, nar- 

 rowly shouldered at the summit and marked by retractively slanting, 

 slender axial ribs, of which 120 occur on the first of the remaining turns, 

 160 on the second, and 150 on the last. These ribs are about one- fourth 

 as wide as the spaces that separate them, and they become expanded at 

 the summit, or else 2, 3, 4, or even 5 may become fused into a large 

 white hollow denticle. The spiral sculpture consists of strong rounded 

 threads, which are of equal distribution and which are about one-third 

 as wide as the spaces that separate them. Of these threads, 6 occur on 

 the first, 7 on the second, and 10 on the last turn. These sculptural ele- 

 ments appear as if the spiral sculpture was the basic sculpture and the 

 axial ribs were superimposed thereon; at their junction with the spiral 

 threads they form slender thickenings, the long axis of which coincides 



