218 R. S. Lull — Fossil Dolphin from California. 



has become converted into a foramen through the closing 

 together of the anterior margins. In Delphinus the lateral 

 edges of the anterior sternal are prolonged into outward and 

 backward projecting cornua, while in the other there are 

 simple rounded angles in their place and the width of the 

 sternal posterior to them is relatively much greater. 



Measurements of the sternum. 



Length of stern als 1 and 2 

 Greatest breadth 



Delphinavus 



Cat. No. 



10040 



120 mm 

 ... 10 



Delphinus 



Cat. No. 



265 



224mm 



84 



I cannot positively identify sternal ribs in the fossil. 



The Appendicular Skeleton. 



Both paddles are preserved, that of the right side almost 

 entire, the left more or less occluded by the skull but supply- 

 ing certain details lacking in the other due to the orientation 

 of certain of the bones, notably the humerus. 



The limb is essentially delphinoid, showing apparently the 

 same reduction of digits, but differing mainly in the more 

 primitive character of the individual elements. In so far as it 

 is preserved, the limb is of approximately the same size in 

 both modern and fossil forms. 



Scapula. — The scapula is less widely expanded than that of 

 Delphinus, otherwise the two are very suggestive of one 

 another. In the fossil the horizontal extent of both coracoid 

 and acromion processes cannot be ascertained ; they are, how- 

 ever, similar in the extent of their origin to those of Delphi- 

 nus. The prescapular fossa seems to have been relatively 

 greater in the ancient type. 



Humerus. — The ratio of humerus to radius is much greater 

 in the fossil, as one would be led to infer in the case of the 

 more primitive form. The humerus is also relatively more 

 slender, but has much the same general outline as in Delphi- 

 nus, except that the tuberosity projects slightly above the 

 head and has a lesser transverse extent. A faint indication of 

 the capitular epiphysis may be seen in the fossil, practically 

 the only indication of one in the entire skeleton. The right 

 humerus presents the impression of its posterior aspect, while 

 the left is viewed from without. The latter shows the charac- 

 ter of the distal facets, each of which is planoconcave, the 

 curved axis lying in the transverse plane. The radial facet is 

 the greater, as in Delphinus. 



Forearm. — The forearm presents perhaps the greatest diverg- 

 ence in the two forms of any part of the limb, for instead of 



