150 American Seashells 



plug dome-shaped with a tiny pimple on one side. Color translucent-tan to 

 light-brown. Old specimens are whitish, often with a purplish stain. The 

 shell has a white band behind the aperture. C. hemphilli Bartsch and C. bakeri 

 Bartsch are probably diminutive forms of this species. The development of 

 the small pimple on top of the dome-shaped plug is variable. 



Subgenus Meioceras Carpenter 1858 



Shells 2 to 4 mm. in length, very bulbous in the middle, smooth, and 

 with an oblique, constricted aperture. Resembles a miniature Cadulus 

 (Scaphopoda). 



Caecum nitidwn Stimpson Little Horn Caecum 



Figure 376 



Southern half of Florida and the West Indies, 



2.0 mm. in length, glassy translucent-white with irregular specks or mot- 

 tlings of chalk-white; bulbous in the center; apex with a lopsided, rounded 

 plug which has a tiny projection on the highest side. 



Caecum lennondi Dall from the west coast of Florida differs in having 

 a single, moderately well-raised, circular hump around the middle of the 

 shell. Uncommonly dredged just offshore. 



Family PLANAXIDAE 

 Genus Flanaxis Lamarck 1822 



Planaxis lineatus da Costa Dwarf Atlantic Planaxis 



Lower Florida Keys and the West Indies. 



/4 inch in length, thick and strong; glossy-smooth when the thin, smooth- 

 ish, translucent periostracum is worn away. Color whitish cream with neat, 

 spiral bands of brown (10 in last whorl, 5 showing in whorls above). Whorls 

 in top of spire with 4 or 5 small spiral cords, later becoming obsolete. Aper- 

 ture slightly flaring, enamel-white with 10 brown dots on the edge of the 

 outer lip. Nuclear whorls very small, glossy, translucent-brown and sharply 

 pointed. 



Subgenus Supplanaxis Thiele 1929 

 Planaxis nucleus Bruguiere Black Atlantic Planaxis 



Southeast Florida and the West Indies. 



H inch in length, resembling a thick, polished, dark-brown Littormu 

 periwinkle. Characterized by 5 strong spiral cords which are developed on 



