PHYSETERID& 247 



yoked together." This name was substituted by Owen for the 

 earlier one Basilosawns of Harlan, with the consent of that author, 

 on the mammalian nature of the animal being demonstrated. 1 The 

 latter name is, however, still generally retained by American 

 zoologists. The remains have hitherto been found chiefly in the 

 Eocene formations of the States of Alabama, Louisiana, Mississippi, 

 and Arkansas, and have been assigned to several species. A portion 

 of a skull is recorded from the Barton Clay (Eocene) of Hampshire, 

 England. 



Subwder ODONTOCETI, 

 the DELPHINOIDEA, or Toothed Whales. 



Calcified teeth always present after birth ; generally numerous, 

 but sometimes a very limited number (in a few cases none) are 

 functionally developed. No baleen. Upper surface of the skull 

 more or less asymmetrical. Nasal bones in the form of nodules or 

 flattened plates, applied closely to the frontals, and not forming 

 any part of the roof to the narial passage, which is directed upwards 

 and backwards. Olfactory organ rudimentary or absent. Hinder 

 end of the maxilla expanded and covering the greater part of the 

 orbital plate of the frontal bone. Lachrymal bone either inseparable 

 from the jugal, or, when distinct, very large, and forming part of 

 the roof of the orbit. Tympanic bone not ankylosed with the 

 periotic, which is usually only attached to the rest of the skull by 

 ligament. Eami of mandible nearly straight, much expanded in 

 height posteriorly, with a wide funnel-shaped aperture to the dental 

 canal, and coming in contact in front by a flat surface of variable 

 length, but always constituting a true symphysis. Several of the 

 anterior ribs with Avell-developed capitular processes, articulating 

 with the bodies of the vertebrae. Sternum almost always composed 

 of several pieces, placed one behind the other, with which several 

 pairs of ribs are always connected by the intervention of well- 

 developed cartilaginous or ossified sternal ribs. External respiratory 

 aperture single, the two nostrils uniting before they reach the 

 surface, usually in the form of a transverse subcrescentic valvular 

 aperture, situated on the top of the head. Manus always penta- 

 dactylous, though the first and fifth digits are usually very little 

 developed. No caecum, except in Platanista. 



Family PHYSETERID^E. 



No functional teeth in the upper jaw. Mandibular teeth various, 

 often much reduced in number. Bones of the cranium raised so as 



1 See Trans. Geol. Soc. ser. 2, vol. vi. p. 67. 



