494 GEOLOGICAL SURVEY OF THE TERRITORIES. 



than in the A. occidentale. If any median incisors exist, they must be 

 small, as the narrow fracture-surface below the original alveolar border 

 exhibits no trace of alveoli. The mandibular teeth are rather elongate, 

 the first having two roots. The ramus has not the incurvature to the 

 diastema seen in S. ?iehrascensis, and is relatively not so deep, and more 

 robust below the last molar than in that species. 



Associated with this mandibular ramus, I found the large part of the 

 skeleton of the same animal and the superior molar dentition of two 

 individuals of the same size. The teeth resemble those of the A. occi- 

 dentale^ but, besides the smaller size, exhibit differences in the structure 

 of the premolars. The first is about as broad as long ; has a strong 

 anterior basal cingulum, and both of the transverse crests strongly 

 curved backward at their inner extremities. The second is transverse, 

 and the transverse crests are simple and distinct distally. The third 

 premolar has its inner anterior angle produced at the base of the crown. 

 The transverse crests form a continuous circuit inwardly, and it is the 

 posterior which curves forward and joins the anterior a short distance 

 external to the inner termination of the latter. In the fourth premolar, 

 the transverse crests are entirely distinct, and the anterior is the longer, 

 causing, as in the third, the protuberance of the inner anterior angle of 

 the shoulder of the crown. Both are bounded at the base by a cingu- 

 lum, which extends round the posterior base to the outer crest. The 

 posterior transverse crest sends forward a process toward (in one speci- 

 men joining) the anterior at one-third the length from its end. The 

 transverse crests of the true molars are simple, and the anterior cross- 

 crest the thickest j no cingula on the inner bases. 



Measurements. 



M. 



Length of inferior molar series 0.172 



Length of premolars only 080 



Length of first premolar 015 



Length from first premolar to end of symphysis .040 



Length of symphysis 048 



Width of symphysis at diastema 040 



Depth of ramus at last molar 050 



Thickness of ramus at last molar 030 



Diameter of inferior incisor 010 



Length of series of superior molars 153 



Length of series of superior premolars 073 



Length of first premolar 013 



Length of fourth premolar 022 



Width of fourth premolar 032 



Length of penultimate molar 037 



Width of j)euultimate molar 038 



The other series of molars presents similar dimensions, and a few 

 slight variations in structure. 



The remainder of the skeleton pertains to one or the other of these 

 individuals. The axis strongly keeled below ; the anterior articular 

 surfaces are widely expanded, and the posterior is concave and oblique. 

 Its neural carina is elongate and elevated behind. The dorsal and 

 lumbar vertebrae are slightly opisthoccelian. The glenoid cavity of the 

 scapula is a broad oval, and the coracoidis quite prominent, but obtuse. 

 The internal condylar tuberosity is strong, the external almost wanting ; 

 the internal distal crest is very strong. The supracondylar fossae are 

 very deep. The radius is a stout bone, and attached to the slender 

 ulna by coarse sutural surface, which is very narrow along the middle 

 of the shaft. The femur is stout, and its large trochanter is recurved 

 anteriorly as well as posteriorly so that both faces are concave. There 



