Weller — Kinderhooh Faunal Studies. 175 



The dimensions of an average specimen are: length 17 mm., 

 breadth 8 mm., and convexity of one valve 3£ mm. 



Led a saccata (Win.). 



PL XV. f. 20. 



Nuculana saccata, Bull. U. S. G. S. 153: 382. 



Original description. " Shell very small, transversely 

 elongate, rostrate at the longer extremity; obtuse, ventri- 

 cose and saccate at the other. Beak abruptly, though mod- 

 erately, drawn out, and but slightly incurved. Ventral side 

 strongly curved, becoming nearly straight toward the rostral 

 extremity. Dorsal region deeply excavated for an escutcheon 

 on the longer side of the beak; hinge plates bearing each 

 six or seven teeth ; greatest thickness of shell between the 

 beaks and the middle. Pit of adductor of short end very 

 deep on its superior border ; the other pit smaller, deepest 

 on its superior border. Surface with fine, indistinct striae of 

 growth . 



Length of an average specimen 7| mm. and width 4 mm. 



Dexiobia ovata ( Hall ) . 



PI. XV. f. 1-2. 



Original description of Dexiobia whitei. " Shell sub- 

 rotund, with a slight anterior obliquity caused by a moderate 

 protrusion of the antero- ventral border, from which, in the 

 right valve, a slight elevation extends to the beak; anterior 

 margin rather straight above. Hinge-line short, regularly 

 curved ; beaks nearly central. Surface marked by fine ra- 

 diating ribs — becoming obsolete toward the umbo — and 

 numerous irregular concentric wrinkles, which are generally 

 more conspicuous in the left valve." 



The dimensions of a large specimen are, height 38 mm,, 

 length 36 mm., convexity of right valve 14 mm. 



Remarks. This species was originally described by Hall * 

 as Cardiomorpha ovata. The reference of the species to 

 the genus Cardiomorpha was erroneous, and Winchell 

 used it as the type of his genus Dexiobia, changing the 

 specific name to whitei. This change of the specific name, 

 however, does not seem to be warranted. The specimens 



* Rep. Geol. Surv. Iowa. I 2 : 522. 



