82 Mammalia, Digestive System. 



advance. The dentition of the Solidicomua follows that of the Cavicomua 

 pretty closely, ^except that the males sometimes hare Canine teeth in the upper 

 jaw (esp. Cennis Muntjak). The Carenticomua presents considerable anoma- 

 lies ; though, agreeably to the rule as to horns above noted, all have Canines 

 in the upper jaw (especially developed in Moschus moschiferus). The Camelidaa 

 have a pair of laniariform Incisors in the upper jaw; the inferior Canines 

 distinct from the Incisors in their laniariform development, and more erect in 

 position than in the ordinary Ruminantia ; and, lastly, the anterior Premolar 

 laniariform in both jaws. 



Cete. All are Monophyoclont, none truly edentulous : for the 

 Balenidae manifest in their foetal state a true dental system, in the 

 shape of a series of minute calcified denticles in an open groove 

 extending along the alveolar border of both the upper and the 

 lower jaws. In no Cete, except the common Dolphin, are teeth 

 implanted in the Intermaxillaries. The primitive seat of the de- 

 velopment of the tooth matrix is maintained longer in the Cete 

 than in other Mammalia ; and, except in the rudimental tusk of the 

 Narwhal, is at no period enclosed in a bony cell : in this respect the 

 Cete offer an interesting analogy to true Fishes. The teeth in the 

 Cete are all of one kind, and usually of a conical shape. 



The Whales proper (Balaenidae) have the footal dentition of the upper jaw 

 succeeded by homy substitutes in the form of plates, terminated by a fringe, 

 situated on either side of the upper jaw, behind each other : the plane of each 

 plate is at right angles with the axis of the skull, and depends vertically from 

 the palatal surface of the maxillary, and of the anterior part of the palatine 

 bones. The lower jaw of the Whale that has passed its foetal existence has 

 neither teeth nor baleen. The plates are shaped like an obtuse-angled triangle, 

 the fringed side being that subtending the obtuse angle ; one side enclosing the 

 angle forms the outer margin of the baleen plate ; the other is hollow and has this 

 cavity filled with baleen pulp, which is formed of parallel descending tubes 

 passing into bristly fibres at the inferior margin of the horny lamina, of which 

 the external or cortical substance of each plate consists ; and is imbedded in a 

 compact sub-elastic substance, attached to the palate. The Sperm "Whale 

 (Physeter) has teeth in both jaws, but they are visible only in the lower jaw, 

 in which they are situated in a wide and moderately deep groove in the dense 

 semi-ligamentous gum. The first formed extremity of the tooth in the young 

 Physeter (Cachalot) is capped with enamel, which however gets worn off when 

 the tooth is fully developed. In Phocoena Orca (Grampus) the laniariform 

 teeth are as large in proportion to the length of the jaws, as in the Crocodile, 

 and are separated by intervals, so that the upper and lower teeth interlock. In 

 the Narwhal two rudimental teeth are enclosed in a horizontal alveolus at the 

 junction of the intermaxillary with the maxillary ; one of which, the left, is in 

 the male further developed into a tusk nine feet long, marked exteriorly by 

 Spiral ridges ; and with a pulp cavity throughout its entire length internally. 



