MAMMALIA. GETACEA. 355 



thus with the interparietal completely separating the parietals 

 from one another. 



The frontals are expanded, forming large bony plates, 

 which roof over the orbits. The zygomatic process of the 

 squamosal is extremely large and extends forwards to meet 

 the supra-orbital process of the frontal; the zygomatic process 

 of the jugal is on the contrary very slender. The face is 

 drawn out into a long rostrum, formed of the maxillae and 

 premaxillae surrounding the vomer and the mesethmoid 

 cartilage. The maxillae are specially large, and extend back- 

 wards so as to partially overlap the frontals. The nasals are 

 always small, and the anterior nares open upwards between 

 the cranium and rostrum. The periotics are loosely connected 

 with the other bones of the skull and the tyrnpanics are com- 

 monly large and dense. The mandible has hardly any coronoid 

 process, and the condyles are at its posterior end. 



There are no clavicles, but the scapula and humerus are 

 well developed. The humerus moves freely in the glenoid 

 cavity, but all the other articulations of the anterior limb are 

 imperfect ; the various bones have flattened ends, and are 

 connected with one another by fibrous tissue, which allows of 

 hardly any movement. Frequently the carpus is imperfectly 

 ossified. 



The number of digits in the manus is generally five, some- 

 times four, and when there are four digits it is the third and 

 not the first that is suppressed. The number of phalanges 

 in the second and third digits almost always exceeds that 

 which is normal in mammals, and the phalanges are also 

 remarkable for having epiphyses at both ends. The pelvis is 

 represented by two small bones which lie suspended horizon- 

 tally at some distance below the vertebral column ; in some 

 cases vestiges of the skeleton of the hind limb are attached to 

 thenl. 



The Cetacea are divided into three suborders. 



232 



