212 MALACOZOA. TROPIOPQDA. LAMELLIBRANCHIATA. 



1 . Cythercea exoleta. — Shell orbicular, subequilateral, 

 moderately convex, with concentric striae, dull yellowish 

 or reddish-white, with radiating reddish or purplish 

 bands. Exoletus, worn. 



2. Cythercea lincta. — Shell suborbicular, inequilateral, 

 moderately convex, with fine concentric strise, glossy, 

 greyish-white. Linctus, licked. 



3. Cythercea unddta. — Shell suborbicular, convex, 

 thin, with numerous concentric striae and larger rugae, 

 the margin sinuous. Undatus, wavy. 



Genus 5. Venus. — Shell suborbicular, subtriangular, 

 or cordato-ovate, moderately convex, concentrically stri- 

 ated ; umbones prominent ; three divergent teeth in 

 each valve. Named after the goddess Venus. Linnaeus. 



1. Venus Casina. — Shell suborbicular, moderately 

 convex, very thick, with concentric elevated thick entire 

 ridges. 



2. Venus rejlexa. — Shell suborbicular, compressed, 

 rather thin, with concentric elevated, reflexed, thin- 

 edged ridges. Bejtexus, bent back. 



3. Venus GaJHna. — Shell cordato-trigonal, moderately 

 convex, concentrically lamelloso-sulcate. Gallina, a hen. 



A. V. Gallina laminosa. Covered with plaits. 



B. V. Gallina stridtula. Marked with small streaks. 



4. Venus Frideauxidna. — Shell cordato-trigonal, rather 

 compressed, concentrically lamellate. Named after Mr. 

 Prideaux. 



5. Venus fascidta. — Shell roundish-trigonal, com- 

 pressed, thick, with broad flattened, smooth, concentric 

 ridges, Fascidtus, banded. 



6. Vhms ovdta. — Shell ovato-triangular, rather thin, 

 divergently ribbed, and reticulated by numerous con- 

 centric striae. Ovdtus, egg-shaped. 



7. Venus triangularis. — Shell subtrigonal, smooth, 

 with three teeth in one valve, and two in the other. 

 Triangidaris, three-cornered. 



Genus 6. Venerufis. — Shell ovate or elliptical, very 

 inequilateral, convex, concentrically striated ; umbones 



