130 



Alii eric an Se ash ells 



may also appear in eastern Florida. It has been named floridana Reeve 1855, 

 rotundata von Martens 1865 and sphaera Pilsbry 193 1. 



Genus Smaragdia Issel 1869 

 Smaragdia viridis Linne 



Southeast Florida, the West Indies and Bermuda. 



Emerald Nerite 



Plate 4h 



/4 to H inch in length, glossy, smooth, pea-green, often with tiny chalk- 

 whice bars and rarely with purplish brown, narrow, zigzag bars. True 

 viridis comes from the Mediterranean. Some workers separate our form as 

 the subspecies viridemaris Maury 191 7. N. iveyssei Russell 1940 is a synonym. 



Order MESOGASTROPODA 



Superfamily LITTORINACEA 



Family LACUNIDAE 



Genus Lacuna Turton 1827 



Rather fragile, smooth periwinkles characterized by a shelf-like colu- 

 mella and a chink-like umbilicus. Periostracum smooth, fairly thin and light- 

 brown. Operculum paucispiral and corneous. Cold-water inhabitants, usually 

 dredged in areas of kelp weed. 



Figure 36. Northern Lacunas, a, Lacuna carinata Gould, ^ inch (Pacific coast); 



b, Lacuna imijasciata Cpr., y^ inch (California); c to e, Lacuna vmcta Turton, 



% inch (both coasts); c, operculum showing reinforcing bar (dotted); d, animal 



showing the penis on the right side; e, radula (a single row greatly enlarged). 



Lacuna vincta Turton Common Northern Lacuna 



Plate 22p-, figure }6c-e 



Arctic Ocean to Rhode Island. Alaska to California. 



^ to % inch in length, 4 to 5 whorls, resembling a Littorina, but charac- 

 terized by its fairly thin, but strong, translucent shell, its shelf-like columella 

 along side of which is a long, narrow, deep umbilical chink. Outer lip fragile. 



