

186 A NEW FOSSIL PORPOISE FROM MARYLAND. 



In 1902, Dr. 0. P. Hay pointed out the fact that the name Phoca wymani 

 really belonged to the seal skull originally described by Wyman in 1850, and 

 could not properly be applied to the teeth from Virginia and Maryland. He 

 renamed the latter Delphinodon leidyi, designating as the type-specimen the tooth 



figured by Leidy in 1869, in the Extinct Mammalian Fauna of Dakota and 

 Nebraska, PL 30, fig. 12. Though this change of name is very unfortunate, in 

 view of the fact that the species has become imbedded in the literature under 

 the designation of wymani, it seems unavoidable under the rules generally 

 adopted to-day. Dr. Hay also, in 1902, fixed upon D. mento as the type of the 



genus Delphinodon. 



The type-tooth of Delphinodon leidyi, as already mentioned, presents a close 

 similarity to those of the form herein described. It seems to leave no room for 

 doubt that the two forms belong to the same genus, and this conclusion involves 

 the corollary that the genus Delphinodon, or at least the species D. leidyi, belongs 

 to the family Delphinidae. This will be more fully considered under the next 



heading. 



Whether the present form is identical specifically with D. leidyi is more diffi- 

 cult to determine. The type-tooth of the latter species is in the museum of The 

 Academy of Natural Sciences of Philadelphia, where it was examined recently 

 by myself. This tooth agrees almost exactly in form with the right lower tooth 

 No. 2 of the Chesapeake Beach skeleton herein described. It has the same 

 ridges in the same relative positions. The crown is flattened anteriorly and 

 posteriorly in similar fashion in both teeth. The antero-exterior ridge bifurcates 

 in the same manner in both teeth and at about the same point, relatively, but 

 the angle of divergence is greater in the type-tooth of D. leidyi. 



The main differences between the two teeth mentioned above are that the 

 type-tooth of D. leidyi is a little larger than that from the Chesapeake Beach 

 skeleton, the crown is rather more incurved, and the posterior branch of the 

 bifurcated antero-extemal ridge is more prominent and more distinctly crenulated. 



In the type-tooth of D. leidyi the root is nearly or quite closed below, indi- 

 cating that it is from an adult individual. The longitudinal furrow shown in 

 Leidy's figure of this tooth, pi. 30, fig. 12, is not a groove but a crack which 

 extends through the crown as well as the root. The little rugosities seen at the 

 upper right edge of the crown in Leidyi figure are part of the external ridge. 

 The protuberance at the lower left edge is a part of the cingulum from which 

 the internal ridge springs. The ridge itself is represented by the dark line o 

 that side of the figure. The figure as a whole is not accurate. The root is ma e 

 to appear too flat, being in reality quite convex, and is curved backward at 

 lower end. The enamel of the crown of this tooth is everywhere rugose, excep 

 as affected by wear, and the rugosity is a little more pronounced than in 

 tooth from the Chesapeake Beach skeleton with which it has been compare 

 above. 



The three additional teeth from Charles County, Maryland, which were 



