I'USSILS OF TUE LOWEK CAKBUNIFEKOUS. 265 



FOSSILS OF THE LOWEIl CARBONIFEROUS. 

 BRACHlOrODA. 



Genus 0RTHI8 Dahuan. 

 Ortiiis kesupinata 'L 



Plato 5, tigs. 1-2. 



Orthis resypiiiata Martin sp. 



Shell of moderate size, transversely elliptical or quadrate-elliptical; 

 valves ventricose, the dorsal quite rounded and almost evenly ventricose, 

 sometimes a little fuller on the umbone ; middle of the valve slightly 

 impressed with a broad, shallow, mesial sinus, extending from near the beak 

 to the front of the valve ; beak proportionally large and full, somewhat 

 incurved, and projecting beyond the line of the hinge ; area moderately 

 large, extending about half the length of the valve, the plane of its surface 

 nearly in the direction of the plane of the valve. Muscular impression 

 large, extending to about two-fifths of the length of the shell, distinctly 

 flabellate and lobed. Ventral valve unknown. Surface marked by moder- 

 ately strong, rounded, radiating striae and concentric lines of growth. 



The species is represented in the collection only by dorsal valves, but 

 the specific characters are unmistakable and easily recognized. 



Formation and locality. — In Lower Carboniferous limestone, near the 

 base of the formation, at Dry Canon, Oquirrh Mountains, Utah. Collected 

 by J. E. Clayton. 



Genus PRODUCTUS Sowerby. 

 Productus Flemin(71 van BukliiXGTonensis Hall. 



Plate r., tigs. "J-12. 



Froduchis Flemingi var. Biirlbiytonemls Ilall, Geol. Kept. Iowa, vol. i, part ii, p. 598, 

 pi. 12, fig. 3. 



Shell of medium size, wider than long; height and length subequal, or 

 a little longer than high, except in old individuals, where the front is much 

 produced, giving additional height; hinge-line as wide, or a little less than 

 the width of the shell below. Ventral valve strongly arcuate, more abruptly 

 curving just posterior to the middle of the valve; auriculations distinct when 



