COAL-MEASURE AND PERMO CARBONIFEROUS FOSSILS. 273 



F0SSIL8 OF THE COAL-MEASURES AND PERMO- 

 CARBONIFEROUS. 



LAMELLIBRANCHIATA. 



Genus AVICULOPECTEN McCoy. 



AVICULOPECTEN WeBERENSIS U. sp. 



Plate VI, fig. 5. 



Shell of medium size or smaller, suborbicular in outline, the length 

 and height being subequal, anterior side of the shell larger than the posterior, 

 giving a slight obliquity to the valves; hinge-line straight, nearly two-thirds 

 as long as the greatest length of the shell, anterior portion forming rather 

 more than one-third of the length. Left valve- very convex, the depth equal 

 to about one-ihird the height when not compressed. Auriculations not dis- 

 tinctly limited, anterior one small, with a shallow rounded sinus below, 

 extremity rounded; posterior side of moderate size, the sinus faintly marked; 

 extremity obtusely angular. 



Surface marked by somewhat irregular radiating costse, which vary 

 much in size, some of them being moderately strong and distant, with from 

 one to four smaller ones between, most prominent and distinct on the 

 median portion of the valve, becoming gradually smaller on the sides and 

 wings. There are also tine concentric striae crossing the radii, giving a 

 slightly roughened surface. Right valve unknown. 



The species resembles in some of its chai-acters many of those referred 

 to Ewnicrotis Hawni M. & H., but differs in the size and form of the wings 

 and in the finer radii of the surface. The character of the auriculations 

 would prevent it from being classed as Eumicrotis. 



Formation and locality. — In limestones of the Upper Coal-Measures 

 (Permo-Carboniferous), foot-hills southeast of Salt Lake City, Wahsatch 

 Range, Utah. Collected by S. F. Emmons, esq. 



AVICULOPECTEN CURTO-CAEDrNALIS 11. Sp. 

 Plate VI, fig. 4. 



Shell of small size, broadly ovate in outline, and nearly equilateral, 

 widest just below the middle of the height; hinge-line short, not exceeding 



18 P R 



