ORAL CAVITY 237 



'angle gland' at the angle of the mouth, which may be the last 

 remnant of the labial glands of the other sauropsida. 



Besides numerous smaller glands (labials, buccals, linguals, 

 palatines) imbedded in the mucous membrane and opening separately 

 into the mammalian mouth, the salivary glands, though absent from 

 the cetacea, form a distinguishing feature of the group. These 

 salivary glands are usually in the neighborhood of the mouth, but one 

 or more of them may be carried back into the neck (fig. 252), but in 

 all cases the homologies are decided by the openings of the ducts. 

 The salivary glands include the submaxillary and sublingual of the 

 lower groups, and in addition the parotid gland, apparently a develop- 



^""^d 



Fig. 252. — Salivary glands of fruit bat, Pleropus conspicillatus (Princeton, 2065). 

 P, pd, parotid gland and duct; rl, rid, retrolingual gland and duct; sm, smd, submaxillary 

 gland and duct. 



ment within the class. The submaxillary normally Ues in the lower 

 jaw beneath the mylohyoid muscle, and its duct (Wharton's duct) 

 opens near the lower incisor teeth. Near this is frequently a retro- 

 lingual gland, its duct opening near the former. The sublingual 

 gland occurs between the tongue and the alveolar margin of the 

 lower jaw and usually empties by numerous duct. The parotid 

 gland has its normal position near the ear, and its duct (Stenon's 

 duct) pours the secretion out near the molars of the upper jaw. 

 Other oral glands are occasionally present, like the molar glands of 

 ungulates and the orbital glands of dogs, both of which have ducts 

 leading into the mouth. 



