Art. 21 TEXAN PLEISTOCENE VERTEBRATES HAY 9 



the lower right third molar, the detached lower left third molar, 

 a detached upper left second molar — and a section of the right 

 maxilla supporting the third molar nearly complete, these parts 

 belonging to one individual. 



The part of the lower jaw preserved is remarkably short and 

 deep. From the front of the tooth row the profile turns downward 

 more abruptly than is usual, even in Maimnut americanuni (pi. 5, 

 fig. 3). The depth of the jaw at the front of the tooth row is 200 

 mm. The lower face of the symphysis forms an ascending curve 

 measuring 150 mm. The hinder face rises perpendicularly a dis- 

 tance of 130 mm. to the lingual gutter. This gutter runs forward 

 a little and then turns rapidly downward to meet the ascending 

 curve of the lower face of the symphysis in the blunt beak. The 

 length of the gutter is close to 190 mm. At its lower end it is only 

 about 25 mm. wide, and it is nowhere more than 45 mm. deep. 

 The lower face of the symphysis is at first flat, but it soon presents 

 two slightly diverging keels separated by a sharp furrow (pi. 5, 

 fig. 2). In this are seen the openings of several foramina which 

 probably transmitted nerves and blood vessels to the lower lip. 



Where the keels and the ridges bounding the lingual gutter meet 

 there is on each side a constricted foramen which opens directly 

 backward into the jaw and has a long diameter of 10 mm. It 

 seems possible that these foramina represent the sockets of vestigial 

 lower tusks; but, as shown by the somewhat injured alveolar ridges 

 bounding the lingual gutter, a canal, which probably transmitted a 

 branch of the inferior dental nerve, opens into the supposed socket 

 through its roof. Possibly the lower portion of the openings is all 

 that remains of the sockets. On Figure 3 of Plate 5 no part of the 

 lingual groove is seen. At the right hand in the lower half of the 

 border a part broken away exposes the canal which transmitted 

 the dental nerve. In Figure 2 on the left side (right in the speci- 

 men) the upper dark spot represents this canal 40 mm. higher up 

 than that taken to be a possible socket. On the side of the jaw 

 in front of the second molar are three openings for exit of branches 

 of the nerve mentioned. 



In the collection is a detached upper left second molar which 

 the writer refers to this species. The great front root supporting 

 the outer end of the first crest is preserved. It has a length of 

 123 mm., with some part of the distal end missing. The base of 

 the root which supported the inner end of the first and second 

 crests remains. The crown has lost the outer half of the first valley 

 and the adjacent part of the second crest. All three crests are 

 worn so that in each the dentine areas of the inner and outer halves 

 coalesced. The pretrite end of the hinder crest is, for some reason, 

 worn deepest. Remains of a trefoil are preserved on the first crest. 

 79653—26 2 



