A NEW FOSSIL PORPOISE FROM MARYLAND. 191 



Among fossil genera already known, the present form most closely resemble* 

 Heterodelphis. It might, indeed, probably be included in that genus, except 

 that in the latter the mandible has a longitudinal furrow on each side, and the 

 teeth have long, slender and smooth crowns. Two species of Hetcroddphis have 

 been described—//", klinderi Brandt and H. leiodonlus Papp. The figures of the 

 former published by Brandt 1 are extremely unsatisfactory, while those of //. 

 leiodonlus published by Papp 2 show that the specimen on which the species was 

 based was so badly broken that scarcely any character is clearly determinable. 

 From Brandt's figures of H. klinderi, however, we learn that that species is some^ 

 what smaller than the present form and that the atlas has a more pronounced 

 median basal facet for the odontoid, and a more descending transverse process. 

 The posterior cervicals are of about the same form, though smaller. The 

 thoracics and lumbars, on the other hand, differ noticeably in that the transverse 

 processes are expanded, as in Inia. The scapula differs widely in form, but it 

 is hardly probable that the figure is accurate. The humerus is similar in general 

 form, but more expanded below. This figure, like the preceding, is probably 

 inaccurrate. 



The tympanic bone is apparently broad at the anterior end as in the present form. 



The differences between H. leiodontus and the present form have been already 

 mentioned. Among the similarities may be mentioned the form of the atlas, 

 which has complete foramina in the sides of the neural arch for the exit of the 

 first pair of spinal nerves and a short, triangular transverse process. The verte- 

 brae appear to be quite similar in the two forms except that the neural spines of 

 the anterior thoracics are strongly inclined backward, as in Tursiops and some 

 other recent delphinoids. The scapula appears to be quite similar in form. The 

 correspondence of the humerus, radius and ulna is very striking, but the major 

 tuberosity of the humerus appears to be higher in H. leiodontus than in the 

 present form and the deltoid ridge, or tuberosity, more salient. The radius is 

 less curved in the former but the ulna appears to have presented indications of 

 the same lunate olecranon found in the present species. 



Dr. Papp convinced himself that H. leiodontus was a very long beaked dol- 

 phin, with 60 teeth or more on either side of each jaw. 3 I do not find anything 

 in the figures or description, however, inconsistent with the view that the rostrum 

 was about as long as in Delphinodon, that the symphysis of the mandible was 

 about one-third the total length of the latter, and that the teeth were about 

 38 on either side of each jaw. 



Dr. Papp assigned the genus Heterodelphis to the family Platanistidae, 4 while 

 Brandt in 1873 had assigned it to the Delphinidae 6 and Dr. Abel, in 1905, to the 

 Acrodelphidae (- Iniidse). 6 



* M£m. Acad. Imp. St. Petersb., ser. 7, XX, 1873, pis. 25, 26. 



* L- c, pp. 49 and 52. 

 4 L- c, p. 60. 



902-6 



! llt m ' Acad ' Imp * ScL St * p ^ ter sb., ser. 7, XX, 1873, pp. v, vi, 226 and 248. 



M6m. Mus. Rov. Hist, Nat R»1<r TTT ion* ~ ion 



