366 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvi. 



Genus PSEPHIDIA Dall, 1902. 



Type, Pse2)hls lordi Baird. 



Shell small, veneriform, polished, with faint concentric sculpture; 

 beaks not prominent; valves inequilateral, with a narrow, feebly 

 defined lunule and no escutcheon; inner margins not crenate; pallial 

 sinus distinct, angular; hinge with three delicate entire cardinals in 

 each valve, but no laterals; animal with the mantle edges fused below, 

 the siphons short, simple; an anterior opening for the foot, which is 

 not byssiferous. 



This group is confined to the Pacific coast as far as known, and is 

 represented in the Pacific Pliocene. It is Pseplm Carpenter, 1864, 

 not of Guenee, Le^ndoptera., 1854. Carpenter named several species 

 without specifying a type in 1864. In 1865 he selected P. lordi Baird 

 as type, and for the first time gave a distinctive diagnosis of the 

 genus. Part of the species, among those originally referred to the 

 group, belong elsewhere. P. tantilJa appears to be a Tra')ise7ineUa, 

 and P. telUrayalls is the neiDionic young of Petricola. 



EAST AMERICAN SPECIES. 

 DOSINIA (DOSINIDIA) CONCENTRICA Born, 1780. 



Florida Keys (Conrad); Martinique, Porto Rico, Guadeloupe, Virgin 

 Islands, Santa Cruz, and St. Thomas, West Indies; Colon or Aspin- 

 wall; Maracaibo to Rio de Janeiro, Brazil. 



The Venus amamtrica of Gmelin is a mixture of various species, the 

 name is fixed by Born's figure, which represents the southern type. 

 The concentTiGa of early American writers was the Z>. discus of Reeve. 

 The D. concentrica of Reeve is the D. elegans of Conrad. 



The present species is Arthemis patagmiica Philippi, 1844; Venus 

 philippii Orbigny, 1847; Venus dilatatu Solander, 1797; and Dosin'm 

 fioridana Conrad, 1866, was probably founded on a 3'oung specimen. 

 D. concentrica is the analogue of the Pacific coast D. ponderosa 



DOSINIA (DOSINIDIA) ELEGANS Conrad, 1846. 



In the oft'shore warm water, near Cape Hatteras, North Carolina; at 

 Charleston, South Carolina; east and west Florida, theTortugas, Texas, 

 and south to Yucatan and St. Thomas, West Indies. 



This fine, flat, and evenly concentrically sculptured species was 

 figured by Lister (pi. 288, fig. 124), and is one of those long confounded 

 under the name of concentrica. The young were referred to D. ohovata 

 Conrad by Miss Bush in 1885. 



DOSINIA (DOSINIDIA) DISCUS Reeve, 1850. 



Cape May, Virginia, and south on the coast of the mainland to Vera 

 Cruz, Mexico. 



