NO. rsv2. SYNOPSIS OF THE VENERID^^DALL. 357 



all belong to CaUithaca. The anterior lateral is so dose to the cardi- 

 nals that it has been counted in with them. The animal is meretriciiie, 

 with long, closel}' united si[)hons. The group u\\ the Pacitie eoast 

 recedes to the P^ocene in time. 



Siablkin.il y VP:]SrERI]Sr^E3. 



A.VTERIOK I.ATERAr, TEETH ABSEXT. 



Genus CYPRIMERIA Conrad, 1864. 



Type, C excavata Morton. Cretaceous. 

 Pallial line feebly fiexuous ]>ehind. 



Sul)genus Cyclorisma Dall, 10()2. Type, Cyclothyris carolinensis 

 Conrad. Cretaceous. 



Pallial line deeply sinuated. 



This is Cych)thyr!s Conrad, 1875; not of McCoy. Brachiopoda, 1844. 



Genus THETIRONIA Stoliczka, 1871. 



Type, Thetis major Sowerby, 1826. Cretaceous. 



Surface granulose; pallial sinus high, angular yertically ascending; 

 no lunule or escutcheon. This is Thetis Sowerin', 1826, not of Oken. 

 1815. 



? Sul^genus Thetiopsis Meek. 1876. T^^pe, T. circular is Meek and 

 Hiyden. Cretaceous. 



Smaller and smoother, the sinus shorter and irregular at its anterior 

 basal part. 



This is Tethiopsis Fischer. 1887. 



Genus MYSIA (Leach MS.) Lamarck, 1818. 



Type, Venus undata Pennant. 



Siphons separated; hinge with two right and three left cardinal 

 teeth; a circuuiiscribed lumile, but no escutcheon. European. 



This is Liicino2)sis For))es and Hanle}^, 1848, but not Myxia Cra}', 

 1847. 



Genus CYCLINELLA Dall, 1902. 



Type, Dosinia tenuis Recluz. 



Three cardinal teeth in each yalye; otherwise like Mysia. American. 



This genus extends to the Oligocene in time. 



Genus CHIONE Megerle, 1811. 



Type, Yenus cancellata Lamarck. 



Three cardinal teeth in each yalye; pallial sinus short, angular; 

 lunule and escutcheon defined, sculpture cancellate, inner margins of 

 the yalves crenate; concentric sculpture dominant. 



Subgenus Chione s. s. Type, V. cancellata Lamarck. 



