138 AjT/erican Seas he Us 



4 to 4.5 mm.; glassy-white; depressed interspaces small, rounded; Texas 

 to the West Indies and Bermuda . sagraiana Orbigny 



Family VITRINELLIDAE 

 Genus Vitrinella C. B. Adams 1850 



Shell minute, thin, depressed, umbihcate, and with 3 to 4 subtubular 

 whorls. The umbilicus has rather flattened walls and is usually bounded by a 

 spiral cord. The rounded aperture is oblique, with a thin lip, its upper margin 

 arching forward. Columella only moderately thickened. Operculum corne- 

 ous, thin, multispiral. There are many species in American waters with 

 quite a number of genera and subgenera. The family is undergoing consid- 

 erable change under the current research by H. A. Pilsbry. We are includ- 

 ing only three examples of this interesting group. Consult recent numbers 

 of The Nautilus. 



Subgenus Vitrinella s. str. 

 Vitrinella helicoidea C. B. Adams Helix Vitrinella 



North Carolina to Florida and the West Indies. 



2 mm. in diameter, planorboid, 4 whorls, spire moderately raised. Trans- 

 lucent-white, glossy, smooth. Umbilicus round, very deep, moderately wide, 

 bounded by a small, spiral, smoothish thread. Wall of umbiHcus flattish. 

 Columella strong, braced on the whorl above by a small, spreading callus. 

 Outer lip thin, sharp. Not uncommon in shallow water. This is the type of 

 the genus. 



Subgenus Circulus Jeffreys 1865 

 Vitrinella multistriata Verrill Threaded Vitrinella 



Plate 17V 



North Carolina to Florida. 



5 mm. in diameter, planorboid, well-compressed, 4 whorls, opaque-white, 

 with a glossy sheen. Outer surface covered with numerous, crowded, spiral, 

 incised lines. Umbilicus with rounded sides, deep, rather narrow. 50 to 100 

 fathoms. Locally common. 



Subgenus Solariorbis Conrad 1865 

 Vitrinella beaui Fischer Beau's Vitrinella 



North Carolina to Florida and the West Indies. 



