ART. 14. THE SKULL OF MEGAPTEBA MIOCAENA KELLOGG. 9 



rides the carina of the vomer to a greater degree than is normal in 

 Megaptera nodosa^ and may possibly have been fused medially to its 

 adjoining mate. A careful comparison of this palatine with the 

 same element in skulls of Megaptera and Balaenoptera shows that 

 this coalescence is a modification of rare occurrence except possibly 

 in Balaenoptera horealis. 



PTERYGOIDS. 



The pterygoids are apparently the most delicate bones in the basi- 

 cranial region of the skull, and for this reason they are often found 

 to be damaged in fossil specimens. The imperfect state of preserva- 

 tion of the scaphoid fossae of this skull prevents one from describing 

 with any degree of certainty the correct outlines of the bones form- 

 ing the ventral surfaces. 



These fossae are large and well defined, ovoidal in outline and 

 comparable in size to those of a young Megaptera nodosa. It is 

 stated by von Schulte" that the so-called pterygoid fossa can not 

 correctly be called such in Balaenoptera horealis and that this cavity 

 should be known as the scaphoid fossa. 



The internal pterygoid commences posteriorly at the anterior mar- 

 gin of the lateral swelling of the basioccipital and is bounded inter- 

 nally by the expanded wings of the vomer. The hamular processes 

 on both sides are destroyed, though the curvature of the descending 

 portion of the internal pterygoids at the fracture indicates that they 

 curved internally and horizontally. The roof of the scaphoid fossa 

 is formed in part by the internal pterygoid, though this element is 

 so intimately anlcylosed to the external pterygoid process of the 

 alisphenoid that accurate determination of their boundaries is im- 

 possible. Von Schulte's statement, as well as his figures ^^ of the 

 external pterygoid process of the alisphenoid in the embryo of 

 Balaenoptera lorealis., are of unusual interest in view of the fact 

 that previous workers considered this element to be the ala tem- 

 poralis, or alisphenoid. In the nasal fossa the vaginal process of the 

 internal pterygoid plate is joined to the vomer by suture. 



In the temporal fossa the external pterygoid process of alisphenoid 

 joins by suture the vertical plate of the palatine and is in contact 

 with the postorbital process of the supraorbital. The foramen ovale 

 is situated in an aperture formed between the diverging glenoid and 

 the falciform processes of the squamosal at their line of union with 

 the posterior termination of the external pterygoid process of the 

 alisphenoid, and more internally is partially bounded by the de- 

 scending lateral wing of the basisphenoid. The external pterygoid 

 process probably forms the floor of the scaphoid fossa. 



" Schulte, H. vou W., Anatomy of a foetus of Balaenoptera borealis, Mem. Amer. Mus. 

 Nat. Hist, 11. s., vol. 1, pt. 6, pp. 476-477, New York, March, 1916. 

 ^ Idem, p. 476, pi, 44, fig. 2. 



