A NEW FOSSIL PORPOISE FROM MARYLAND. 



187 



referred to D. wymani ( = D. leidyi) by Cop 



the Acad em 



tion. There is no apparent reason for disputing the correctness of this assign- 

 ment, although these specimens differ in various details from the type-tooth 

 The one figured by Leidy in pi. 30, fig. 10, is extremely similar to the lower 

 left tooth No. 3 of the Chesapeake Beach skeleton, but is much larger and has 

 the postero-internal ridge much more pronounced and distinctly crenulatcil, or 

 tuberculated. This gives the former tooth the breadth shown in Leidy's figure. 

 Otherwise, in its curvature, in the position of the ridges, in the rugosity of the 

 enamel, etc., the two teeth are practically identical. In Leidy's fig. 10 the 

 antero-external ridge is on the left margin of the dark oblong fracture and above 

 the latter it forms the outline of the crown. 



The tooth shown in Leidy's fig. 11, which is another of the Charles County 

 teeth assigned to D. leidyi by Cope, shows distinct traces of anterior and posterior 

 longitudinal ridges, but the enamel is worn nearly smooth. 



Another of these Charles County teeth exhibits traces of the postero-internal 



ridge, but not of the antero-external one, and the enamel is worn quite smooth 



This tooth and the preceding one look a little more massive than the type and 



the tooth represented in Leidy's fig. 10, but they have the crowns blackish like 

 the type. 



A tooth in the National Museum which was picked up from the shore at 

 Chesapeake Beach, and is numbered 1118, is almost a duplicate of the type of 

 D. leidyi, but from the opposite side of the mouth. The crown is a little shorter 

 and the root a little thicker and the antero-external ridge more strongly crenu- 

 lated. The latter is apparently not bifurcated, but as the enamel is worn nearly 

 smooth this cannot be determined accurately. There is a slight constriction at 

 the upper end of the root in the type-tooth of D. leidyi which is not found in 

 the other tooth, but this appears to be due to wear. 



The National Museum collection contains another tooth from Chesapeake 

 Beach (in vial marked 1244-1247) which is almost the exact counterpart of 

 Leidy's fig. 10. The ridges are the same and in the same positions, but the 

 tuberculation of the postero-internal ridge is worn away and that of the antero- 

 external ridge is very indistinct. The two teeth mentioned are practically identical 



in size. 



Dimensions op Teeth of Delphinodon leidyi. 



Measurements. 



Type. Mio- 

 cene of Vir- 

 ginia. Leidy, 

 pi. 30, fig. 12. 



Charles Co., 



Maryland. 



Leidy, pi. 30, 



fig. 10. 





Total length 



Length of crown ", , . " . 



Greatest diameter of crown 

 at base 



Oreatest diameter of root '. '. '. 

 Diameter of root at lower 

 extremity 



1 Root defective. 



mm. 



30.0 



9.0 



7.0 

 6.5 



mm. 

 28.0 1 

 10.0 



Charles Co., 



Maryland. 



Leidy, pi. 30, 



fig. 11. 





mm. 

 33.0 

 10.0 



8.5 

 7.0 



8.0 

 8.0 



Charles Co., 



Maryland. 



Third Tooth. 



U. S. N. M 



No. 1118. 



Chesapeake 



Beach, Md. 





. 



U.S.N. M. 



No. 1244-1247. 

 Chesapeake 

 Beach, Md. 



mm. 

 38 

 10 



8.5 

 7.0 



mm. 



30.5 



9.2 



G.5 

 5.9 



3.5 



4.0 



4 + 



2.5 



2.4 



mm. 



24.2 1 



9.4 



7.0 

 6.4 



3.0 



