Digestive System Special. 75 



Form. Each Incisor has a prominent posterior hasal ridge : the middle pair 

 are generally larger than the lateral Incisors ; and all four bear a larger propor- 

 tion both to the entire skull and to the rest of the teeth than in Bimana. The 

 Canines of the Baboons are deeply grooved in front, like the poison fangs of 

 some Snakes. The Premolars as well as the Molars are severally implanted by 

 one internal and two external fangs. 



Tlatyrrldna. Number. Have four more teeth in the Molar series than the 



3 3 



Catarrhina, viz. p m ^5-^. The ' Marmosets/ however, have but two true Molars 



2.21.1 2.2 

 on each side of both jaws, their dental formula being i n""^; <^ T~\ > f^ T~o' 



Form. Molars have blunt tubercles. 



3.3 33 



Lemuridcv. Number. Incisors are commonlv ' , and Premolars ' 



^ 3 . 3 3 . a 



2 2 

 (Lichanotus), or in number. Situation. In the upper jaw of Otoclinus 



and Lemur the small Incisors are vertical. Form. The Incisors are generally 

 modified somewhat toward the Eodent and Marsupial type, the inferior onea 

 are long and narrow. The Molars have sharp tubercles. The dentition of 

 Cheiromys (Aye Aye) is modified in analogical conformity with the Eodent 

 type, to which it makes a very close approximation, in the absence of Canines, 

 and, the wide vacancy between the single pair of scalpriform Incisors and the 

 short series of Molars ; it may be distinguished from that of Eodentia in that 

 a. the crowns of the upper incisors project obliquely forward, and do not extend 

 vertically downward (Rod.) ; b. the lower Incisors are more curved, and c. all 

 the Incisors are entirely invested with Enamel, which is however thicker upon, 

 the front than upon the back part of the tooth. 



Inseetivora. The dental system in this Order is remarkable for 

 the many varieties and even anomalies which it presents ; almost 

 the only characteristic predicable of it being the presence of 

 sharp points or cusps upon the crowns of the molar teeth. Struc- 

 ture. The teeth consist of a basis of hard Dentine, with a thick 

 coronal investment of Enamel (especially in Soricidae), and the usual 

 outer covering of Cement : around the fangs the Cement usually 

 assumes the character of true bone, traversed by medullary canals. 

 Replacement. The Deciduous teeth of the Talpidas and Soricidae 

 are uterine, i.e., are developed and disappear before birth. JVumier. 

 Two species in this Order have the * typical' number of teeth, viz., 

 Talpa and Gymnura, each having the dental formula 

 ^.3.31.1 4.4 3.3 



'STS'^ITI'^^ 474' ^3"T3 = ^^- 

 Chrysochlore approaches, in the number of its Molar teeth, the 



remarkable condition which a solitary genus of existing Marsupials; 

 (Myrmecobius) also presents ; judging from the form of the teeth, it 



has at least r~~^ true Molars. In Ehynchocyon (African Shrew) 



