GENERAL CHARACTERS 227 
Teeth are generally present, but exceedingly variable in number. 
In the existing species they are of simple, uniform character, all 
having conical or compressed crowns and single roots, and are never 
preceded by milk-teeth. They are therefore homodont and 
monophyodont. In one group, the Mystacocetes, the teeth are 
absent (except in the foetal condition), and the palate is provided 
with numerous transversely placed horny lamine or “baleen.” 
The salivary glands are rudimentary or absent. The stomach is 
multilocular, its structure being fully noticed under the genus 
wa IP Fp 
Fic, 75.—A section of the skull of a young Dolphin (Globicephalus melas). x}. PMzx, Pre- 
maxilla; Mz, maxilla; ME, ossified portion of the mesethmoid; an, anterior nares; Na, 
nasal; IP, inter-parietal; Fr, frontal; Pa, parietal; SO, supraoccipital; Hx0, exoccipital. 
BO, basioccipital; Sq, squamosal; Per, periotic; AS, alisphenoid; Ps, presphenoid ; Pt 
pterygoid ; pn, posterior nares; Pl, palatine; Vo, vomer; s, symphysis of mandible; id, 
inferior dental canal ; ep, coronoid process of mandible ; cd, condyle ; a, angle; sh, stylo-hyal ; 
bh, basi-hyal ; th, thyro-hyal. (From Flower’s Osteology of Mammalia.) 
Phocena. The intestinal canal is simple, and only in some species 
provided with a small cecum. The liver is very little fissured, and 
there is no gall-bladder. The vascular system is greatly complicated 
by arterial and venous plexuses, or retia mirabiliv. The larynx is of 
peculiar shape, the arytenoid cartilages and the epiglottis being 
much elongated, and together forming a tubular prolongation, which 
projects into the posterior nares, and when embraced by the soft 
palate produces a continuous passage between the nostrils and the 
trachea, as in Ungulates, but in a more perfect manner. The 
