Maryland Geological Survey 359 



Description. — Teeth robust, elongate, acuminate, sigmoidal; crown 

 conical, somewhat laterally compressed ; with a large robust quadrangular 

 fang expanding gradually to the base, which is divided by a broad basal 

 cleft or sinus extending antero-posteriorly and deepest posteriorly. 

 Lateral basal margins grooved or fluted. Pulp cavity expanded within 

 the fang, closed below and narrowing toward the crown. 



These teeth which apparently represent a large, powerful carnivorous 

 sphyrsenoid fish are rather widespread in the North American Upper Cre- 

 taceous. They are referred to the entirely extinct genus Ischyrhiza Leidy, 

 of which the present species is the type, and are known only from detached 

 and broken teeth. The latter with their large fangs and expanded 

 bipartite base are very characteristic. Two or three species have been 

 described, but it is uncertain whether or not the obviously slight variations 

 that have been recorded are of specific value. The present species was 

 described originally from New Jersey where it ranges from the Matawan 

 into the Monmouth or perhaps Eancocas. It occurs in the Pedee forma- 

 tion of North Carolina and in the Eutaw of Ripley of Mississippi. It has 

 also been recorded from the Ashley marls in South Carolina, where it may 

 have been mechanically reworked from older deposits. 



The Maryland material well illustrates the range of variation. The 

 largest specimen which has lost most of the crown has an indicated length 

 of between 5 cm. and 6 cm. The crown at the base is 12.5 mm. in antero- 

 posterior diameter and 12 mm. in transverse diameter. Eight millimeters 

 above the base the lateral compression has made the proportion of the two 

 diameters as 10 to 7. The fang is 3 cm. long and about 1.7 cm. square at 

 the base. The smallest specimen is represented by the basal part of the 

 fang which in this case is only 5 mm. square. 



Occurrence. — Matawan Formation. Post 105, Chesapeake and Dela- 

 ware Canal (minimum sized form). The large specimen figured is 

 labeled " Matawan formation. Prince George's County," without further 

 detail. Since the bulk of the materials in this county formerly considered 

 Matawan are now known to be of Monmouth age, it seems probable that 

 this tooth came from the Monmouth formation. 



Collection. — Maryland Geological Survey. 



