130 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 105 



which is concave from end to 'end, and wider posteriorly than an- 

 teriorly. The shaft of the rib is flattened anteroposteriorly between 

 the tuberculum and the angle, almost ovoidal in cross section near 

 the middle of its length, and noticeably flattened near the extremity. 

 The length of this rib in a straight line is 306 mm. 



The neck of the sixth rib (pi. 10, fig. 5) resembles that of the fifth 

 rib, and the shaft is similarly flattened between the tuberculum and 

 the angle. The capitulum is rounded. The tuberculum unfortu- 

 nately was destroyed during excavation of this specimen. 



A single-headed rib (pi. 10, fig. 9) lacking the distal end may have 

 articulated with the tenth dorsal. The proximal articular surface of 

 this rib is somewhat convex, the shaft is thickened between this 

 facet and the angle, and below the angle it is distinctly flattened on the 

 outer surface for a distance of about 60 mm. 



Another single-headed rib (pi. 10, fig. 6) from the posterior end of 

 the series on the right side has a large proximal articular surface, a 

 sharp crest approximately 30 mm. in length on the anterosuperior 

 margin behind the articular head, and an ill-defined angle below which 

 the shaft becomes progressively flattened and develops a ridge on the 

 anterior and posterior margins. 



SCAPULA 



It will be noted that the lower portion of this left scapula (USNM 

 20659) is quite unlike the scapula of Inia geqffrensis. The neck of 

 this scapula (pi. 11, fig. 4) is short and rather broad and the glenoid 

 cavity for the head of the humerus is rather shallow. The lower or 

 axillary margin is directed backward and slightly upward from the 

 short neck. The direction and length of this margin suggests that 

 the upper portion of the scapula was rather broad. Since the external 

 surface of this bone is slightly depressed posterior to the assumed 

 position of the spine, a shallow postscapular fossa is indicated. The 

 basal portion of the acromion process is rather broad. The laterally 

 flattened coracoid process lacks the distal end and is directed inward 

 and apparently slightly upward from the neck of the scapula. 



II. PELODELPHIS GRACILIS, NEW GENUS, NEW SPECIES 



Our present knowledge of the cetacean fauna of the Calvert forma- 

 tion of Maryland indicates that in addition to the more frequently 

 occurring long-beaked porpoises of the genera Eurhinodelphis, Schizo- 

 delphis, and Zarhachis, at least one other porpoise with a lengthened 

 rostrum was present during that period in the Chesapeake area. It 

 is now certain that remains of a number of genera and several families 

 of Cetacea were present in the marine Miocene Calvert formation. 



