76 Mammalia. Digestive System, 



the upper Incisors are absent ; the premaxillary bones terminating in 

 a trenchant edentulous border, as in the true Euminant. Situation. 

 In Galeopithecus the two anterior Incisors of the upper jaw are 

 separated by a wide interspace. In Chrysochlore the true Molars 

 are separated from each other by vacant intervals, as in many Rep- 

 tiles. Fixation. In the Shrew the roots of the lower Incisors 

 become anchylosed to the jaw-hone, a Eeptilian character oJffered by 

 the Soricidse alone in the Mammalian Class. Form. The crowns 

 of the first two Incisors of Galeopithecus present the form of a 

 comb, and are in this respect unique in the Class Mammalia : the 

 second upper Incisor presents the peculiarity of an insertion by two 

 fangs. In Amphisorex and Ehynchocyon the lower Incisors are 

 notched, or bilobed. In Chrysochlore the three anterior teeth in the 

 upper jaw, situated in the premaxillary bone, and therefore ' In- 

 cisors,' are laniariform. The crowns of the Molar teeth are gene- 

 rally bristled with sharp points or cusps, and are always broader in 

 the upper than in the lower jaw. In Chrysochlore the crowns of 

 the upper true Molars assume the form of thin plates, narrowed 

 from before backward, with two notches on their working edge, and 

 a longitudinal groove along the outer and thicker margin ; the lawer 

 true Molars are of unusual length. 



Cheiroptera. Replacement. The Deciduous teeth make their 

 appearance above the gum before birth, as in Soricida), but they 

 attain a more completely developed state, and are retained till a 

 short time after birth. Numler. Incisors may be present as 



2.21.1 



o , or :j r, or absent. Canines are always present in both jaws. 



6 . 6 



The Molar series never exceeds r -^ and in the Yampire is re- 



2.2 

 duced to - -. Form. Incisors, when present, are always very 



small, and, in the upper jaw, commonly unequal : in Chilo- 

 nycteris the mid-incisors above and the outer ones below have the 

 crown notched : in Phyllostoma the mid-pair above are large and 

 laniariform: in Desmodus they are two in number in the upper 

 jaw, with large, compressed, curved, and sharp-pointed crowns. The 

 Canines are always of the normal form. The Molar series are 

 bristled with sharp points in the great bulk of the Cheiroptera. 

 In Desmodus (Vampire) the true Molars with the bristled crowns 

 are absent, and the Molar series have simple compreBsed conical 



