474 MAirUAL 01 THE MOLLUSCA. 



Synonyms, Meretrix, Gray. Dione, Megerle. Cryptogramma, 

 Morch. 



Examples, C. dione, PI. XX., Fig. 8. C. chione, Fig. 14, 

 p. 26. 



Shell like Venus; margins simple; hinge with 3 cardinal 

 teeth and an anterior tooth beneath the lunule ; pallial sinus 

 moderate, angular. 



Animal with plain mantle-margins ; siphons united half-way. 



Distribution, same as Venus. Eecent 113 species. 



Fossil, 80 species. 



Merge, Schum. 



Etymology, Meroe, an island of the Nile. 



Synonyms, Cuneus (part) Megerle (not Da Costa). Siinetta, 

 Link. 



Ty^ye, M. picta (=Venus Meroe, L. Donax, Deshayes). 

 PI. XX., Fig. 9. 



Shell oval, compressed ; anterior side rather longest ; hinge 

 with 3 cardinal teeth, and a long narrow anterior tooth ; lunule 

 lanceolate ; ligament in a deep escutcheon. 



Dlstrihution, 11 species. Senegal, India, Japan, Australia. 



Trigona, Miihlfeldt. 



Etymology, trigonos, three-cornered. 



Tyi^e, T. tripla, PI. XX., Fig. 10. 



/SAe/i trigonal, wedge-shaped, sub -equilateral; ligament short, 

 prominent ; cardinal teeth 3 — 4, anterior f remote ; pallial 

 sinus rounded, horizontal. 



Distribution, 28 species. West Indies, Mediterranean, Senegal, 

 Cape, India, West America. 



Fossil, Miocene — . Bordeaux. 



T. crassatelloides attains a diameter of 5 inches, and is very 

 ponderous. 



Sub-genus, Orateloupia, Desm. G. irregularis, PI. XX., 

 Fig. 11. 



Shell sub-equilateral, rounded in front, attenuated behind; 

 hinge with 1 anterior tooth, 3 cardinal teeth, and several small 

 posterior teeth ; pallial sinus deep, oblique. Fossil, 4 species. 

 Eocene — Miocene. United States, France. 



Artemis, Poll. 



Etymology, Artemis, in Greek mythology Dianft. 

 Type, A. exoleta, PI. XX., Fig. 12. 

 Synonym, Dosinia, Scopoli. 



