32 CRETACEOUS AND TERTIARY FISH. 



About three existing - and 39 fossil species have been referred to 

 this genus. 



Isurus desorii (Agassiz). 



Oxyrhina minutus (nee Agassiz) Cope, Proc. Amer. Philos. Soc. Phila., 

 XIV, 1875, p. 362. (Cumberland Co. Miocene.) 



Anterior teeth narrow, robust, much elevated and thick. 

 Crown slightly curved inwards towards apex. Outer coronal 

 surface more or less flattened, and inner well convex. Apex 

 scarcely deflected. Cutting-edges entire. No basal cusps. Root 

 thick, concave or flattened on outer surface, inner face with large, 

 pronounced, bulging or convex surface, and each end a long 

 divergent branch, often unequal and acute. Lateral teeth more 

 compressed, root shorter and with more diverging ends, crown 

 narrow, apex scarcely deflected, and usually entire cutting-edges 

 gradually divergent to ends of base. Length varies to 54 mm. 



According to Woodward this species differs from the existing 

 Isurus oxyrinchus only in the less curvature of the lateral teeth. 

 From worn and fragmentary examples of Lamna elegans, in 

 which the inner coronal striae seem to be obliterated, I cannot 

 distinguish some material positively. Frequently the teeth of 

 Isurus are more or less depressed basally on their inner surfaces. 

 It is also almost impossible to distinguish the teeth of Lamna 

 cuspidata, and no doubt a number of the teeth of the present 

 species may be listed under that name. This form is known only 

 from the detached teeth. 



Formation and locality. A number of examples in the collec- 

 tions of the Academy from the Cretaceous marls, all without 

 beds indicated, are: 1 tooth from "New Jersey" (E. D. Cope), 

 2 teeth from Deal [probably from Manasquan marl, K.] 

 (Breed), 1 from Monmouth County (C. C. Abbott) and 8 more 

 from the same region (W. Cleburne), 3 from Burlington 

 County (T. A. Conrad), 5 from Vincentown [Manasquan marl 

 or Vincentown limesand, K.] (T. M. Bryan), 2 from 5 miles 

 from Mullica Hill (Abbott) and 1 from the latter locality [Nave- 

 sink-Hornerstown marl, K.] (J. Da Costa) and 7 from Alio- 

 waystown in Salem County (H. C. Yarrow). 



