-562 CETACEA. 



Fam. 2. Physeteridae. With functional teeth in the lower jaw only ; 

 asymmetry of skull strongly marked. The maxillary and frontal bones 

 are spread out and produced so as to form on the upper and anterior 

 surface of the skull a basin, which is loaded with fat. The pterygoids 

 have palatal plates, and the mandibular symphysis is elongated. The 

 lacrymals are large and usually distinct. Most of the cervical vertebrae 

 are ankylosed. The posterior ribs lose their tubercular attachment, 

 but retain the capitular, a process arising on the centrum to meet the 

 latter. Fossil forms are known from the Eocene onwards in Europe, 

 America and Australia. 



Sub-fam. 1. Physeterinae. Sperm-whales. With an enormous 

 head, swollen to the extremity by the accumulation of fat (sperma- 

 ceti) ; upper jaw without functional teeth, though functionless teeth 

 embedded in the gums are present ; mandibular teeth set in a groove, 

 not in sockets. Lacrymal bone not distinct. Cranial basin filled 

 with spermaceti. Physeter L., cachalot or sperm whale; one species, 

 P. macrocephalus L., from 55 to 60 feet, the female being smaller ; 

 zygomatic process of the jugal thick ; in all tropical and sub-tropical 

 seas ; food consists principally of cephalopods ; it has a large throat ; 

 ambergris, a concretionary substance, is a product of and found in 

 the alimentary canal of the cachalot, and has great commercial value ; 

 spermaceti and sperm oil are obtained from this whale ; the sperma- 

 ceti is found mixed with the fat all over the body where fat occurs, 

 but the principal accumulation is in the cranial basin. Kogia (Cogia) 

 Gray, with smaller head, slender jugal, teeth in upper jaw absent 

 or only two ; length 10 feet ; rare form, Southern Ocean, Madras, 

 and N. Pacific. Extinct genera, Diaphorocetus Am., U. Eocene, 

 America, Physodon Gerv., Hoplocetus Gerv., and other genera from 

 the Miocene onwards. 



Sub-fam. 2. Ziphiinae. With only one or two pairs of fully 

 formed teeth in the mandible, the rest concealed in the gums ; anterior 

 part of mesethmoid usually ossified ; lacrymal distinct ; feed on 

 cephalopods. Hyperoodon Lacep., bottlenose, skull with largely 

 developed maxillary crests in the male, with spermaceti in upper 

 part of head, length 30 feet ; N. Atlantic ; tb<*y dive deep for food, 

 remain under some time; jump out of tru; water and return head 

 first; fossil in the Red Crag. Ziphius Cuv., Mtsoplodon Gervais, 

 Seas of N. and S. Hemispheres and in Red Crag. Berardius Duver- 

 noy, N. Zealand seas. Extinct genera from the Miocene onwards. 



Fam. 3. Squalodontidae. Extinct forms from the Eocene, Miocene*, 

 Pliocene and possibly Pleistocene, known by their teeth and skulls ; 

 with teeth in the premaxillae and heterodont dentition, i $, c }, p %, m^; 

 the premolars conical and one-rooted ; the molars compressed, ser- 

 rated, especially posteriorly, and two-rooted. The skull like that of 

 other Odontoceti with reduced nasals, and posteriorly placed nostrils. 

 Squalodon Grat., Miocene and onwards ; Prosqualodon Lyd., Eocene, 

 Patagonia ; Phococetus Gerv., Eocene, France. 



Fam. 4. Platanistidae. Fluviatile or estuarine, in the Ganges and 

 rivers of S. America. Rostrum much elongated and narrow, upper and 

 lower jaws with numerous conical one-rooted teeth, premaxillae without 

 teeth, mandibular symphysis very long, orbit very small, lacrymal distinct, 

 cervical vertebrae all separate ; the tubercula and capitula of the ribs 



