190 A NEW FOSSIL PORPOISE FROM MARYLAND. 



in Steno, but were recently noticed by myself, and confirmed by Lonnberg, in 



Delphinapterus . 



The skull somewhat resembles that of Phocozna, especially in the nearly verti- 

 cal position of the nasal bones and the thinness and flatness of the orbital plates 

 of the maxilla and frontals. It presents a marked difference, however, in that 

 the premaxillse are broad and flat, or a little concave, in front of the nares, and 

 extend backward to the outer side of the nasals. In its general conformation, 

 the skull presents a close resemblance to Sotalia, but in the latter genus the 

 orbital plate of the maxillae is thickened anteriorly and strongly bent upward 

 posteriorly, while the nasals are placed high and directed upward rather than 

 forward. The vertical position of the nasals in the fossil form and their slight 

 projection over the nares should probably be regarded as a primitive character 

 rather than as indicating any close affinity to Phocama. 



The symphysis of the mandible, which is short in most recent delphinoids, is 

 long in the present genus. Taken alone, this character cannot, in my opinion, 

 be regarded as indicating an affinity with the recent and fossil inioid dolphins, 

 platanistids, or eurhinodelphoids, especially in view of the fact that in the 

 recent delphinoid genus Steno the symphysis is also long. 



The earbones are typically delphinoid, and differ from those of Phoccena 

 chiefly in proportions, but it must be remembered that those of Squalodon are 

 not very different from the former. The form of the hyoid is also delphinoid. 



The separation of the atlas and axis naturally reminds one of such genera as 

 Prosqualodon j Eurhinodelphis , Inia, Delphinapterus, Monodon, Platanista, etc. 

 In all but the last two, however, there are two transverse processes on each side 

 instead of a single one. Monodon also presents rudiments of a second process, 

 and Platanista is too far removed from the present genus in other respects to 

 merit attention in this connection. 



The erect neural arch and spine of the thoracic vertebra of the present genus 

 find a counterpart in Phocama, among recent delphinoids. They remind one also 

 of the same parts in the genera Eurhinodelphis and Prosqualodon. The lumbars 

 and caudals resemble those of delphinoids, in contradistinction to the ziphioias, 

 physeteroids, etc. , 



The scapula presents a resemblance to that of Inia, but as previously remarked 

 (p. 184) this is probably due to the incompleteness of the acromion, which in its 

 original form is quite likely to have had the form characteristic of the delpnmoi 

 genera. The humerus, though longer proportionately than in most re 

 dolphins, is essentially of the same form as in those genera. It cannot be aen > 

 however, that the rather high larger tuberosity reminds one of Eurhinodelpm^ 

 while the straight shaft is not unlike that of Berardius. The radius is 

 curved than in modern delphinoids, and the ulna more slender, while the a 

 open space between them is not characteristic of that group, but rather of var 

 genera in other groups, such as Berardius, Inia, Platanista, Physeter, etc. 

 olecranon of the ulna is of a peculiar lunate form , resembling that of the zip 

 Berardius and Ziphius, rather than the delphinoids. 



