HISTORY OF WHALES 



181 



may be regarded as an early stage in the 

 development of conditions like those 

 now seen in the mysticetes. The maxil- 

 lary has an infraorbital process that 

 projects backward to the level of the 

 optic canal, and the ascending process 

 has not been pushed backward very far 

 ; over the upper surface of the supraorbital 

 process of the frontal. In its essential 

 features this bone is typically the inter- 

 locking sort of maxillary found in all 

 known whalebone whale skulls. A sub- 

 sequent constriction of the ascending 

 process of the maxillary would lead to the 



presence of pterygoid fossae for accessory 

 air sinuses of the inner ear and a backward 

 infraorbital extension of the maxillary are 

 prerequisites for any precursor of the 

 mysticetes. The presence or absence of 

 teeth on the rostrum, which is unknown, 

 while interesting is of relatively little 

 importance, for embryology shows us that 

 the predecessors of the mysticetes were 

 toothed whales. In another important 

 detail, this skull resembles those of 

 whalebone whales, for it has a periotic 

 bone with a long apophysis wedged in 

 between the exoccipital and the squamosal. 





Pal. 



Fig. 15. Lateral View o* Archaeodelphis patrius, Upper Eocene 

 Dotted lines indicate course of narial passages, narial cavity, and olfactory foramina 



mysticete type of construction. The base 

 of the ethmoid and the dorsal nasal 

 cavities are roofed over by the nasal 

 bones, and the palatine bones do not enter 

 into the composition of the anterior walls 

 of the narial passages, thus agreeing with 

 the type of structure present in the 

 mysticetes. The upper portion of the 

 supraoccipital shield is destroyed, but it 

 is evident that it has not extended forward 

 far enough to meet the frontal. The 

 parietals therefore form the vertex of the 

 braincase. This skull has rather large 

 pterygoid fossae, which agree in shape and 

 position with those of mysticetes. The 



At least one survivor, Patriocetus, of 

 the archaic toothed whales has been 

 found in the Aquitanian white sands of the 

 Linz basin in Austria, along with Ceto- 

 tberiopsis, the oldest known member of a 

 family of primitive whalebone whales, 

 the Cetotheriidae, and Agriocetus, whose 

 exact relationships are still imperfectly 

 known. The imperfect type skull and 

 another fairly well preserved skull form 

 the basis for Patriocetus gratelowpii, which 

 was thought by Professor Abel (1913) to 

 be a precursor of the Mysticeti, but both 

 are so coated with grains of sand that the 

 sutures are obscured. 



