388 THE PCTERCO EPOCH 



The angle of the lower jaw is not reflected nor inflected. A part of 

 the condyle with adjacent regions shows several features. The coronoid 

 process rises near the condyle, and in precisely the same plane as the angle 

 of the jaw. Both leave the condyle near its inner extremity. The articular 

 face of the latter looks upwards and backwards about equally, and is rather 

 flat. 



A fragmentary skull shows a postglenoid crest, and the robust post- 

 tympanic and paroccipital processes united, and leaving the meatus audi- 

 torious externus widely open below. The os petrosum is small and not 

 inflated. The foramen ovale is not separated from the meatus auditorius 

 below. There is a postglenoid foramen, and a supraglenoid foramen There 

 is also a well-marked mastoid foramen. The mastoid bone is extensively 

 exposed. The cranial walls are thick. 



Such part of the cast of the brain as appears, gives the following points: 

 The hemispheres are very narrow, and rather elongate, and are separated 

 by a long flat crus from the olftictory lobes. The latter are very large and 

 nearly as wide as the hemispheres. 



The posterior three premolars are preceded by temporary teeth in both 

 jaws. Of these the anterior is protruded at about the same time as the first 

 true molars, and is the last one shed, remaining until after the last true mo- 

 lar is fully protruded. The last milk premolar diflers from the coirespond- 

 ing permanent one in its gi-eater elongation. The extension is posterior, in 

 the form of a heel with three tubercles, of which the median is very small, 

 the crown resembling a permanent true molar, except that the anterior por- 

 tion is a little more elongate and compressed. The anterior basal lobe is a 

 mere elevation of the cingulum, as in the permanent premolar, lint the 

 internal cusp is more distinct than in the latter. The penultimate milk pre- 

 molar is more like the corresponding permanent tooth, l)Ut is a little more 

 flattened and elongate, and the heel is not tubercular. The first milk molar 

 is a little more compressed than the corresponding i)ermanent tooth, and the 

 edge of the heel is not tubercular. Otherwise they are sinular. It was on 

 a specimen supporting the last two milk molars, with the first true molar so 

 injured that its true character could not be ascertained, that the Periptychus 

 carinhlcns was established. 



