112 Marine Shells of the Western Coast of Florida 



Rarely, specimens of a dark-green color are found. This color- 

 ation seems not to be due to any extrinsic cause. 



Not uncommon on grassy bottoms of littoral zone. 

 Family NEKITIDAE 



Special interest attaches to the Neritidae on account of their 

 adaptation to diverse conditions of environment. Some of its genera 

 are exclusively marine and prefer rocky stations, some are restricted 

 to brackish water, others are fluviatile, while some are able to main- 

 tain themselves for long periods without wetting. The animals are 

 herbivorous and have the unusual habit of placing their eggs upon 

 their own shells and those of other mollusks. 



The shells are globular or subglobular with the body whorl 

 more or less expanded, the spire short and inconspicuous, semi- 

 lunar aperture and simple outer lip. The operculum is calcareous 

 and is furnished with an apophysis which articulates with the op- 

 posite portion of the columella. 



Genus SMARAGDIA Issel, 1869 

 Smaragdia viridisi^'* weyssei Russell PI. 22, figs. 144a, b 



Alt., 8; diam., 5 mm. Shell small, smooth, translucent, obliquely- 

 oval, subglobular, imperforate; color grass-green or yellowish green, 

 unevenly maculated with white in an interrupted longitudinal ar- 

 rangement; a narrow, sharp pencilling of dark-maroon color usually 

 outlines the white spots on the side toward the apex or toward the 

 columella; occasionally some black appears in the color pattern 

 and some few specimens are unicolored. A thin, glossy epidermis gives 

 an appearance of elegance to this small shell. The apex is minute, 

 scarcely elevated, about two whorls, body whorl much enlarged 

 and expanded. Aperture simple, semilunar, outer lip thin, sharp; 

 columella oblique, finely denticulate; translucent callus. Operculum 

 greenish, overlaid with a polished, translucent callus. Operculum 

 calcareous, green, nucleus excentric near lower-inner margin, a strong 

 bifid apophysis at lower columellar angle and a longitudinal fossa in 

 the columella margin. 



The animal is green, with eyes placed at outer bases of pointed, 



i'*5 Gr., smaragdos, emerald; Lat., v'triJls, green. 



