320 
PEPJSSODACTYLA. 
as the last premolar, and suj)ports three true molars. The latter are worn, 
indicating' the full age of the animal. They still retain the enamel surface 
of the sinus between the posterior and median transverse crests, and the 
lower end of the sharp inner margin of the anterior transverse crest. 
While the ramus exhibits the comj^ressed form seen in A. megalodus and 
A. oneridianus, it differs from these and the A. crassus in many striking 
respects. Thus the inferior margin near the angle does not exhibit the protu¬ 
berance and following contraction of the inner side seen in the first two spe¬ 
cies. In another feature, it differs from all the other species, i. e., in the form 
of the ascending ramus. This rises very gradually from the basis of the last 
molar, leaving a subhorizontal edentulous space behind the latter as long as 
the second true molar; its anterior face, instead of being flat and bounded 
by strong lateral angular ridges, as is the case in A. crassus and the two 
other species, is rather narrowly convex. Instead of the usual ridge of 
the outer side, the anterior border of the area of insertion of the masseter 
muscle is marked by a prominent curved protuberant margin, which is 
wanting in the three other species, the surface in them being plane. Behind 
the condyle is seen the tuberosity characteristic of the Bhmoceridce. The 
internal pterygoid fossa is well marked. Rugosities for insertion of the 
lower border of the masseter muscle are strong. The relations of the den¬ 
tition of this species are also peculiar. Tlie last molar is nearly half as large 
again as that of specimens of A. megalodus and A. meridianus of similar 
dimensions of ramus, and the teeth diminish in length anteriorly more rapidly 
than in width. Thus, while the first true molar is as long as in the two 
species named, the width is between one-half and one-third greater. There 
are no external nor internal basal cingula. 
Measurements, 
M, 
Length of the ramus from the fourth premolar (behind) to middle of masseteric 
fossa...... 0.240 
Length of the series of true molars... 0.148 
Length of the first true molar... 0. 044 
Width of the first true molar... 0. 033 
Length of the third true molar .. . 0. 058 
Width of the third true molar. 0,035 
Diameter of the ramus at the first molar. 0.080 
Depth of the ramus at the third molar. .. 0, 092 
