GREGORY: NOTHARCTUS, AN AMERICAN EOCENE PRIMATE 



215 



Notch between Vertical Plate of Pala- 

 tine and Maxilla 

 Expansion of Brain 

 Bulla? 



Sagittal Crest 

 Mandible 



Symphysis. 



Ramus 



Angle 



Condyle 



Coronoid process 

 Ental Excursion of ^landible 

 Brain 



Notharctus 



Open 



Gentle 



Small 



Present 



Of moderate lengtli 

 Moderate, ending beneath p4 

 Shallow 

 Primitive 



Moderately con\ ex 

 Large, high 

 Moderate 

 IVIacrosmatic 



Propithecus 

 {]') Con\'erted into a tunnel 



{F) Pronounced 

 (P) Fairly large 

 (R) Absent 

 (P) Very short 



(P) Very long, ending beneath m-: 

 (P) Deep 



(P) Greatly expanded 

 (P) Strongly con\-ex 

 (P) Short 

 (P) Pronounced 

 iP) Microsmatic 



The available evidence indicates that the deciduous dental formula of Notharctus was the same as 

 it was in Adapts. With regard to the dental formula of Propithecus the writer is inclined to agree with 

 Flower and especially with Lydekker, who would interpret the adult formula as 



If Ct Pi Mi; rather than l| Cn Pi Mf (Leche). 



The detailed resemblance of the lateral lower procumbent front tooth to the true canine of Lepi- 

 dolemur seems too close to be due to convergence; it means only that one pair of incisors persists in the 

 Indrisidse in accordance with their general tendency to reduce the ante-molar dentition. For similar 

 reasons the first premolariform lower tooth, which articulates with the posterior edge of the upper canine, 

 is p2, not p3. The deciduous dentition of Propithecus, Indris, Avahis is fully figured by Grandidier and 

 Milne Edwards. The deciduous lower front teeth, as in the adult, comprise a single pair of incisors and 

 a pair of procumbent incisiform canines. The vestigial low-crown tooth, the first of the cheek teeth, 



Fig. 79. Young skull and lower jaw of Pro jiithi 



' rrau.rl. After Milne Edwards. X f. 



The external walls of the alveolar proces.s and of the mandible have been removed to show the unerupted permanent teeth. In 

 the upper jaw the following teeth arc in use: di\ di-, dc, dp\ dp\ M' is coming into place; the permanent canine, the two premolars 

 and w^, are embedded in the jaw. In the lower jaw the following teeth are in use: di, dc, pi, dp,, dps, dpi. Mi is about to erupt, 

 ni2, nii are buried in the jaw. 



