408 PALAEONTOLOGY OF NEW YORK. 



Spathella ventricosa. 



PLATE LXVI. FIGS. 41, 42 



Oiikmiota milrinKia, Wiiitk ami Whiti-iki,I). Proc. Boa. Soc. Nat. Hist., vol. viii, p. 297. 1862. 

 SiiugiihioliltK rtulriitixtm (W. an<l W.), S. A. Millkr. Cat. Am. Pal. Foss., p. 2"3. 1877. 

 Ill part " " " Hall. Pal. N. Y., vol. v, pt. 1. Plates ami Explanations : PI. 66, 



tiffs. 36-42. 1883. 



Sheli, of medium size, elongate, siil)-cyliiidrical, widest behind ; lengtli more 

 than twice the height ; basal margin nearly straight, scarcely arcuate in the 

 middle, curving into both extremities. Posterior extremity abruptly rounded. 

 Cardinal line nearly straight, about half the length of tlie shell, parallel to 

 the basal margin. Anterior end very short, abruptly rounded below. 



Valves very convex, gibbous along the middle and in the umbonal region. 



Beaks anterior, not prominent, small and closely incurved. Post-umbonal 

 slope rounded, gibbous. 



Surfiice marked by fine concentric striae, which are fasciculate, or sub- 

 lamello.se, upon the umbonal and posterior regions. Interior unknown. 



The two specimens described measure respectively 2G and 35 ipm. in 

 length, and 12 and 16 mm. in height. 



This species resembles the preceding, in many respects, but the anterior end 

 is .shorter, the valves are more gibbous in the anterior portion, and the lanielli- 

 form stria? are not so strongly m.arked. 



Formation and locality. In the Yellow sandstones, at Burlington, Iowa. 



