446 PROCEEDINGS OF THE NATIONAL MUSEUM. tol. 49. 



CYATHODONTA GALAPAGANA, new species. 



Shell small, elongate, white, the anterior end the longer; left valve 

 rather convex, bearing a smooth narrow escutcheon, the remainder 

 of the surface covered with very numerous (50-55) narrow, close-set, 

 hardly obhque plaits; a single narrow ray borders the escutcheon; 

 granulation not perceptible under an ordinary magnifier; the hinge 

 hnear, very weak; the truncation obhque, inconspicuous; the posterior 

 end bluntly rounded below, the anterior end narrower, rounded; the 

 umbo rather prominent; paUial sinus subquadrate, ascending, just 

 reaching the vertical from the beak in the left valve. Length of left 

 valve, 27; posterior end to vertical, 10; height, 18; diameter of left 

 valve, 5 mm. 



Distribution. — Type locality, near the Galapagos Islands at station 

 2813, in 40 fathoms, sand, dredged by Bureau of Fisheries steamer 

 Albatross. Cat. No. 195029, U.S.N.M. 



Only one left valve of this species was obtained. 



The following unnamed Atlantic species may properly find a place 

 here: 



CYATHODONTA CRUZIANA, new species. 



Shell small, thin, white, covered with a dehcate straw-colored 

 periostracum ; valves unequal, moderately convex, the anterior end 

 longer, the posterior end truncate, the whole covered with a coarse 

 granulation irregularly, rather densely distributed; on the anterior 

 dorsal slope of the right valve the plaits are obsolete, as they also are 

 on the posterior dorsal area, which is not bordered by a distinct ray 

 in front; between these areas the plaits (30-35) are continuous and 

 fairly regular with subequal interspaces; on the anterior dorsal area of 

 the left valve they reach practically to the margin; on this valve 

 there are a median and a posterior obscure ray, the latter in front of 

 the posterior doi-sal area; liinge with a feeble ligament over a separate 

 strong resihum, with a purse-shaped lithodesma in front of the 

 resihfer; paUial sinus small, rounded, not reacliing the vertical from 

 the beaks. Length, 25; posterior end to the vertical, 10; height, 13; 

 diameter of right valve, 6; of the left valve, 3.5 mm. 



Distribution. — Type locality, near Santa Cruz Island, West Indies, 

 in 38 fathoms at station 127; dredged by U. S. S. Blake. Cat. No. 

 64429, U.S.N.M. 



This very neat Httle species is analogous to C jpedroana in the 

 Pacific fauna. 



The following forms allied to Thracia are known from the Pacific 

 coast: 



ASTHENOTHAERUS VILLOSIOR Carpenter, 1864. 



Manuel Lagoon, Lower California, to Cape St. Lucas. 



BUSHIA PANAMENSIS Dall, 1889. 



Station 2805, in 51 fathoms, mud, Panama Bay, U. S. S. Albatross. 



