176 VENERID^. 



Yenus, Linn. 



Syn. — Antigona, Schum., 1817. 



Distr.- — 176 sp. World-wide. Low-water — 140 fathoms. V. 

 astartoides, Behring's Sea. V. ve^^rucosa, Britain, Mediterranean, 

 Senegal, Cape, Red Sea, Australia ? Fossil, 200 sp. Oolite — ; 

 Patagonia, United States, Europe, India. V. verrucosa, Linn. 

 (cxiii, 7, 8). V. puerpera, Linn, (cxiii, 9). 



Shell thick, ovate, smooth, sulcated, or cancellated ; margins 

 minutely crenulated ; cardinal teeth 3 — 3 ; pallial sinus small, 

 angular; ligament prominent ; lunule distinct. 



Animal with mantle-margins fringed ; siphons unequal, more 

 or less separate ; branchial orifice sometimes doubly fringed, 

 the outer pinnate ; anal orifice with a simple fringe and tubular 

 valve ; foot tongue-shaped ; palpi small, lanceolate. 



MERCENARiA, Schum., 1817. (Crassivcnus, Perkins, 1869.) 

 Shell thick, ventricose, cordiform ; margins crenulated within ; 

 three compressed, diverging teeth in each valve, the posterior 

 of the right valve and anterior of the left valve strong and 

 slightly bifid, the others lamellar ; pallial sinus subtriangular. 

 An American group, containing some of the largest and heaviest 

 species of the genus. V. tridacnoides, a fossil of the United 

 States, has massive valves, ribbed like the clam-shell. The North 

 American Indians used to make coinage (wampum) of fragments 

 of Venus rtiercenaria (cxiii, 10-12) by perforating and stringing 

 them on leather thongs ; this is the edible hard-shell clam largely 

 consumed on and near the coast of the United States. 



CRYPTOGRAM MA, Morch, 1853. (Anomalocardia, Schum., 1817. 

 Triquetra, Blainv., 1818.) Shell ventricose, triangular, prolonged, 

 flexuous and attenuated posteriori}^ ; hinge with three cardinal 

 teeth in each valve, the anterior one of the right valve small ; 

 margins crenulated. F. niacrodon, Lam. (cxiii, 13). V. squamosa, 

 Linn, (cxiv, 30). 



CHiONE, Megerle, 1811. (Murcia, Romer, 1867. Omphalo- 

 clathrum, Klein.) Shell oval, triangular or subcordiform ; margins 

 flneljr crenulated ; hinge narrow, solid, with three teeth in the 

 right valve and two in the left, the anterior tooth longest ; liga- 

 ment narrow ; pallial sinus shallow. Mantle-margins folded and 

 dentate; siphons short, unequal, the branchial doubly eirrated, 

 the anal ciliated. V. giiidia, Bvod. (cxiii, 14^. 



ciRCUMPHALUS, Klein, 1753. Surface of the valves lamellar. 

 V. plicata, Grmel. (cxiii, 15,16^. 



TiMOCLEA,- Leach, Brown, 1827. (Leucoma, Homer, 1867.) 

 Surface decussately striate. V. grata, Sa}^ 



CHAMEL^A, Klein, 1753. Surface concentrically striate. V. 

 aphrodinoides, Reeve (cxiii, 17). 



VENTRicoLA, Bomer, 1867. Surface concentrically lamellate. 

 V. rugosa, Chemn. 



