54-0 



NORTH AMERICAN INDEX FOSSILS. 



margin, prominent, turned forward. Lunule large, deeply and 

 sharply impressed. Surface crossed by numerous, regular, con- 

 centric undulations. Average measurements of two types : length 

 and height 20 mm. ; length 26 mm., height 20 mm. 



Queen Charlotte Islands, Vancouver. 

 498. A. trapezoidalis Stanton. (Fig. 738.) Comanchic. 



Fig. 738. Astarte (?) trapezoidalis, right and cardinal views. (After Stanton. ) 



Shell elongate, marked with a broadly rounded umbonal ridge 

 and crossed by prominent, subangular, concentric ridges. 

 Knoxville : California. 



CXXXVIII. Opis Defiance. 

 Trigonal cordate, smooth or concentrically striate, with pro- 

 nounced epidermis. Beaks prominent, curving strongly so as to be 

 .concave forward. Lunule very deep, bordered by a keel. Cardi- 

 nal teeth very long, narrow ; one in the right valve, two in the left. 

 Triassic-Cretacic. 

 499. 0. calif ornica Stanton. (Fig. 739.) Comanchic. 



Fig. 739. Opis cali/ornica, two views of the right and one of the left valve. 

 (After Stanton.) 



Surface marked with fine growth lines and more distant, irregu- 

 lar, concentric furrows. 



Knoxville : California, Oregon. 



CXXXIX. Crassatellites Kruger. 

 Shell solid, attenuated behind. Umbos small, close together. 

 Lunule distinct. Resilifer present beneath the umbo. Hinge 



