ART. 17 MOLLUSKS FROM "WYOMING EEESIDE AND WEYMOUTH 7 



j^oung of Ostrea prudentia White, but it is not possible to be sure 

 of their identity. 



Family ANOMIIDAE Gray 

 Genus ANOMIA Linnaeus 



ANOMIA species 

 Plate 1, Figures 2, 3 



Two moulds of the exterior of valves represent a species of Anomia 

 with but little sculpture. 



Valve subcircular in outline, with cardinal margin nearly straight, 

 however; umbones marginal or almost so, inconspicuous. Surface 

 ornamented by concentric lines of growth and a few distant and 

 rather faint radial lines. Internal characters entirely unknown. 



Length of jarger specimen, 19 millimeters ; height, 18 millimeters. 



Such forms as this are much alike at widely separated horizons, 

 and in the absence of better material it seems of little value to apply 

 a specific name or attempt comparisons. 



Cat. No. 73764, U.S.N.M. 



Family ANATINIDAE Dall 

 Genus PERIPLOMYA Conrad 



PERIPLOMYA? ASPEN ANA, new species 



Plate 1, Figure 1 



A single natural cast of the exterior of a left valve is similar to 

 Periplomya applicata Conrad.^^ As noted by Wade, some of the 

 European forms assigned to Thracia are not very strikingly different 

 from Conrad's species or the present one, and the status of the genus 

 P&riploTivya and its species should not be considered settled until 

 more is known about them. Though the material in hand is scant 

 foundation for a new species the shell is sufficiently characterized to 

 deserve a name. 



Valve depressed, elongate-oval in outline and nearly symmetrical, 

 with an oblique carination extending posteriorly from the beak. 

 No fissure visible in the beak of the type, though shell is entirely 

 absent. Sculpture is even over entire valve, consisting of rather 

 distant concentric lines parallel to the margin. Internal characters 

 entirely unknown. Length, 44 millimeters; height, 25 millimeters; 

 depth of valve, as preserved, about 5 millimeters. 



" Wade, Bruce, The fauna of the Ripley formation on Coon Creek, Tcnn. : U. S. Geol. 

 Survey Prof. Paper 137, p. 75, pi. 24, flg. 3, 1926. Wade erroneously designates this 

 species Periploma, but it is the genotype of Periplomya Conrad (Amer. Journ. Conchology, 

 Tol. 3, p. 15, 1867; vol. 6, p. 76, 1870). 



