A NEW FOSSIL PORPOISE FROM MARYLAND. 



183 



differing from the last chiefly in the less extended and thicker inferior extremity 



The dimensions are as follows 



Measurements. 



a 



b 



e 



Greatest depth 



Greatest breadth superiorly 



Greatest breadth inferiorly 



Distance between centers of articular facets 



mm 

 13 

 14 

 18 

 10 



mm. 

 28 

 10 



14 

 [141 



I 



mm 

 27 

 12 

 20 

 17 



The wl 



Ribs. 



(Plate XXIV.) 

 portions, of more than 21 ribs are preserved. Tl 



of pairs originally present cannot be determined, but it exceeded eleven 



The 



first eight pairs appear to have possessed both head and tubercle, as in many 

 recent delphinoids. 



Portions of both of the ribs belonging to the first pair are preserved. They are 

 thin, broad and flat, and are somewhat tapering distally. One rib of the 2d 

 pair is practically complete. This is a little thicker than the first one at the 

 proximal end and nearly as broad. It tapers distally but is expanded again 



the distal end and terminates 



thickened, oval facet for articulation 



with the sternal cartilage. The centers of the head and tubercle are separated 

 by an interval of 24 mm. The third pair is similar to the second, but longer 

 and more slender. The neck is shorter on each succeeding pair, and appears 

 to end on the eighth pair, the posterior ribs having a single, large, rounded facet 

 at the proximal end. Three such ribs belonging to the left side and one belonging 

 to the right side have been preserved. 



The dimensions of some of the ribs are as follows: 



Measurements. 



A. 



1st 

 Rib, 

 Left. 



Total length in a straight line 

 Greatest breadth at angle 



mm. 



\ 



Greatest breadth near middle of length . 

 Greatest breadth at inferior extremity . 

 Greatest breadth immediately above 1 

 inferior extremity 



Distance between centers of tubercle 

 and head 



Greatest thickness of rib near the 

 middle 



Greatest thickness at the inferior 

 tremity 



18 

 13 



B. 



2d Rib, 

 Left. 



C. 



3d Rib, 

 Left. 



mm. 



189 

 17 

 12 

 15 



mm. 



215 

 14 

 10 

 14 



P. 



4th 



Rib, 



Right. 



mm. 



E. 



5th 

 Rib, 

 Left. 



mm. 



F. 





Left. 



Q. 



Right 



H. 



Left. 



I. 



Uft 



J. 



Left. 



18 



24 



15 



22 





ex- 



3 



3 



8 



3 



8 



24 



11 

 8 



mm. 



15 



9 



8 



mm. mm. mm. mm. 



9 



22 



4 



21 





5 



4 



20 



9 



7 



8 

 6 





10 

 10 



12> 





5 





9 1 



5 



7 



i 



4 



Scapula. 



The right scapula, which (except for a few fragments) is the only one pre- 

 served, is practically complete (PL XXV, fig. 1). It resembles that of Inia and 



1 Breadth of superior extremity. 



