MARYLAND GEOLOGICAL SUEVET 81 



Occurrence. — Choptank Formation. Jones Wliarf, Flag Pond. 

 Calvert Formation. Plum Point, Fairhaven, Charles county near the 

 Patuxent river. 



Collections. — Maryland Geological Survey, Johns Hopkins University, 

 Philadelphia Academy of Natural Sciences, Museum of Comparative 

 Zoology. 



OxTRHiNA sillimani Gibbes. 

 Plate XXX, Fig. 7. 



Oxyrhina sillimani Gibbes, 1847, Proc. Acad. Nat. Sci. Phila., vol. iii, p. 368. 

 Oxyrhina sillimani Gibbes, 1849, Jour. Acad. Nat. Sci. Phila., 2nd ser., vol. i, p. 



302, pi. xxvii, figs. 165-168. 

 Isurus sillimani Hay, 1903, Bull. 179, U. S. Geol. Survey, p. 307. 



Description. — Teeth attaining a total height of about 3 cm., and 

 exhibiting much uniformity. Distinguished from 0. hastalis by the 

 greater thickness of the crown, which is slightly convex on its outer 

 surface, and by having a deeper and more expanded root with divergent 

 branches. Coronal apex sometimes curved backwards, but never bent 

 out of the vertical plane. 



This species occurs in about equal frequency with 0. desorii, which 

 it accompanies. The example figured is one of the lateral teeth and 

 shows the characteristic form of the root which serves to distinguish 

 this species from 0. hastalis. 



Occurrence. — Calvert Formation. Plum Point, Fairhaven, Charles 

 county near the Patuxent river. 



Collections. — Maryland Geological Survey, Philadelphia Academy of 

 Natural Sciences, Museum of Comparative Zoology. 



Oxyrhina minuta Agassiz. 



Oxyrhina minuta Agassiz, 1843, Poiss. Foss., voL iii, p. 38.5, pi. xxxvi, flgs. 36-39. 

 Oxyrhina minuta Gibbes, 1849, Jour. Acad. Nat. Sci. Phila., 3ud ser., vol. i, p. 302, 



pi. xxvii, figs. 161-163 (non fig. 164). 

 Isuriis minutus Hay, 1902, Bull. 179, U. S. Geol. Survey, p. 306. 



It is doubtful if the imperfect teeth from the Eocene of South 

 Carolina assigned to this species by Gibbes properly belong here, and 

 it is practically certain that the species is wrongly recorded by Cope as 

 occurring in the Miocene of Maryland and New Jersey. The specimens 



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