246 



DOUGLASS FOSSTL MAMMALIA 



respects. P^ is much larger and more complex, but it may be a temporary tooth. There are 

 quite prominent antcro-external cusps on the last two premolars and the first two molars. 

 Superior Dentition.—?* has four sharp cusps, three of which— the protostyle, pro- 

 tocone and tritocone— are in an anteroposterior line. The protocone is the largest and is 

 high and pointed. The tritocone is larger than the protostyle. The deuterocone is oppo- 

 site the interval between the protocone and tritocone. This tooth is the longest of those 

 that are preserved in the upper jaw. 



P 4 -, like the molars, is wider than long. It has four primary cusps— the protocone, 

 tritocone, deuterocone and tetartocone— and three secondary ones— a protostyle and an 

 anterior and a posterior median conule. The protocone and tritocone are high and 

 pointed, the first being slightly the higher. The tetartocone is prominent but not high. 

 The protostyle forms a small hut distinct antero-external cusp. The protoconule and 

 metaconule are plainly distinguishable (with a lens) on the protoloph and metaloph. 



M 1 is almost like Pi except that it is wider and the protoconule is merged into the 

 protoloph which passes from the protocone to the parastyle. The metaconule is distin- 

 guishable. There is a small metastyle. M y is wider than M 1 but not so long. There 

 is only a trace of a metastyle. M" is small. The anterior elements are well developed, 

 but the hypocone and metacone are much reduced. 



Inferior Dentition.— The only premolar that is preserved is just erupting and is 

 somewhat injured. 



In all the molars the anterior cusps are much higher than the posterior ones. The 

 protoconid and metaconid are connate at the base and the paraconid appears as a small 

 anterior median cusp. The protoconid and metaconid are of a, nearly equal height' In 

 the heel or talonid the hypoconid is somewhat larger— has a greater antero-posterior 

 diameter than the entoconid. The hypoconulid is median and small. The other molars 

 are formed in the same pattern, but they decrease slightly in size posteriorly. 



The infraorbital foramen opens above M 1 , is narrow transversely and opens diagon- 

 ally upward. It is in a longitudinal concavity which extends backward a short distance 

 on the anterior part of the zygomatic arch. The posterior part of the foramen is only a 

 little in advance of the anterior of the orbit, At the anterior upper margin of the orbit 

 is a quite large protuberance. 



The horizontal ramus of the mandible is narrow vertically. The angle projects 

 downward and backward, the posterior angle being slightly hooked upward. The con- 

 dyle is just above a line passing through the highest points of the molars. It is disk- 

 shaped, the broad articular surface facing backward as much as upward. The coronoid 

 process is broad. The tip is broken off. The anterior angle of the masseteric fossa is 

 considerably behind the last molar and below the alveolar border. It is quite deep and 



