VERTEBRATES. 105 



This species bears a strong resemblance to S. grandis, but is more elongated 

 in form and is entirely without the wrinkles and folds that conspicuously mark 

 that species, a character which is regarded of even generic value (though, as 

 we think, unwarrantably,) among the similar forms of Cochliodus and Deltodus. 



Figures 6, 7 and 8 represent dextral and sinistral specimens, or those from 

 opposite jaws, of the natural size. 



Formation and locality: Keokuk limestone, Warsaw, Illinois. 



Sandalodus grandis, N. and "W*. 



PL X, Fig. 9. 



Teeth large, thick and massive ; 5 inches long, 1 inch, 8 lines 

 wide at broadest part, 9 lines thick; broader end somewhat 

 rounded, with an obtuse lateral angle ; narrower extremity 

 produced into a moderately long, obtuse point, from which a 

 distinct, though not prominent ridge runs along the line of the 

 axis of the tooth to about its middle. Crown surface strongly 

 arched, both transversely and longitudinally, near the broader 

 end, roughened by lines of growth and fine longitudinal 

 wrinkles; elsewhere smooth and highly polished, finely and 

 uniformly punctate. 



The specimens from which the preceding description was taken, may be only 

 old and fully grown teeth of S. Isevissimus, but they are more rounded at the 

 broader end, more strongly arched and show numerous distinct wrinkles and 

 lines of growth, while in S. Isevissimus the entire crown surface is smooth and 

 highly polished. As has been before suggested, the massive sub-quadrate tooth 

 which we have named provisionally Cochliodus? crassus, coming from the same 

 beds and showing a similar surface, may possibly have belonged to the same 

 fish with the teeth under consideration. 



Figure 9 is taken from a specimen in the collection, which is complete with 

 the exception of the angular terminus of the broader extremity. The strongly 

 marked longitudinal ridge shown in the figure is in part due to the wear to 

 which the tooth was subjected while in the jaw, and consequently somewhat 

 exaggerates that character. 



Formation and locality: Keokuk limestone, Warsaw, Illinois. 



—14 



