Cyrenidae and Gouldiidae 59 



Order TELE0I)ES3L4tEA6T 



Family CTREjVIDAEss 



In general the Cyrenidae are fluviatile and brackish water mol- 

 lusks. Most abundant in temperate regions. 



Genus POLTMESODA Rafinesque, 1S20 



Subgenus PSEUDOCYRENA Bourguignat, ]S55 



Polymeso(la69 floridaiia (Conrad) PI. 9, fig. 5.3 



Alt., 17; length, 21 mm. Shell and margin rounded, smooth, 

 lusterless, thin epidermis; white to purple, often banded in the two 

 colors; umbos rounded, near together; hinge with three cardinal 

 and two lateral teeth; interior smooth, colored like exterior; two 

 muscle scars, simple pallial line. 



Found on tidal flats and in bayous. 



Polymesodsi floridanu protexta"" (Conrad) PI. 9, fig. 54 



Similar to P. jloridana, longer, slightly keeled posteriorly, ven- 

 tral margin has posterior sinuosity. 



Family GOULDIIDAE^i 



The family Gouldiidae is generally distributed through all seas. 

 Species of the genus Crassinella are found from New England south- 

 ward to the West Indies and in the Gulf of Mexico. 



Genus CRASSIXELLA Guppy, 1874 

 Crassinella mactracea"^ (Linsley) PI. 9, figs. 55a, b 



Alt., 8; length, 9 mm. Shell small, flattened, triangular, equi- 

 valve, thin epidermis; brownish red with darker brown; flattened, 

 concentric ribs; umbos apical; two cardinal teeth in left valve, one in 

 right valve; two lateral teeth in each valve; interior smooth, often 

 two broad purple rays; two muscle impressions; simple pallial line; 

 smooth margins. 



From less than one to six fathoms. 



^^ Gr., teleos, complete; dcsmos, band, ligament. 



®^ Gr., Cyrene, a nymph. 



^^ Gr., combining form poly, many, and incso, in middle. 



'^ Lat., pro, before and textus, structure. 



^1 Named for A. A. Gould, M.D., naturalist. 



^- Gr., maktra, a kneading trough. 



