PELECYPODA—TELEODESMACEA. 5 5 5 



Onondaga : New York, Ohio, Michigan, Ontario. Also more 

 rarely in the Hamilton. 



532. P. lirata (Conrad). (Fig. 760, b.) Devonic. 

 Smaller than P. elliptica and more uniformly marked with less 



angular concentric ridges. 



Hamilton : New York— Iowa, Ontario. More rarely in the 



b p# 



■'; ■'. .. ' 



c 



FlG. 760. a, Paracyclas chemungensis; b, P. lirata; c, P. ohioensis, right valve ; 

 d, P. elliptica, left valve. (Pal. N. Y., V.) 



Onondaga. Abundant in Portage of New York and Pennsylvania. 



533. P. chemungensis Hall. (Fig. 760, a.) Devonic. 

 Differs from P. elliptica in its more prominent beaks and in the 



finer more regular concentric striae. 



Chemung Group : New York ?, Pennsylvania. 



CLIV. Lucina Bruguiere. 

 Shell thin, rounded, convex or lens-shaped, slightly inequilat- 

 eral, equivalve. Shell substance porcelaneous or chalky. Lunule 

 deep and narrow ; no visible escutcheon present. An oblique fur- 

 row extends from the umbo to the posterior border. Hinge, usually 

 with two cardinal teeth and one or two lateral in each valve ; either 

 the lateral or cardinal may be absent. Ligament and resilium 

 deeply inset but visible. Anterior adductor scar elongated and 

 placed mostly within the pallial line. Pallial line entire. Surface 

 concentrically striated. Triassic-Recent. 



A. Small — diameter less than .35 inch I. 



I. Posterior fold present 538. Z. smithi. 



I. Posterior fold not present 539. Z. curta. 



B. Of medium size — diameter about .5 inch II. 



II. Cardinal margin nearly straight 1. 



I. Concentric undulations large and distant 535. Z. cretacea. 



I. Concentric undulations small and closed 534. Z. subundata. 



II. Hinge line rounded 537. Z. aquiana. 



C. Large — diameter over I inch 536. Z. occidentalis. 



