168 University of California Publications in Geology [Vol. 10 



MANDIBLE 



A number of mandibles together with separate rami, some of which 

 are directly associated with crania, are also in the collections of 

 the Museum of History, Science and Art. These exhibit the degree 

 of variation already discussed in connection with the University of 

 California series of lower jaws. 



In general the ramus decreases noticeably in height from the base 

 of the coronoid process to the anterior side of the first lower tooth. 

 Occasionally, as in no. 696, the height of the ramus in front of the first 

 tooth is much greater, and resembles M. garmani and 31. robustus as 

 well as no. 21576 Univ. Calif. Coll. Palae. In no. 696, also, the inferior 

 dental canal of the right ramus opens anteriorly by three foramina. 

 The latter variation from the normal number of two occurs quite 

 frequently, much more so than the occurrence of only a single open- 

 ing. The greatest predental width of the mandible is always less 

 than the distance between the first tooth of each side. 



Unfortunately there are do mandibles directly associated with the 

 three exceptionally slender skulls. An incomplete and badly worn 

 mandible, showing the complete lower dentition on one side is, how- 

 ever, associated with no. 695. This specimen exhibits a remarkable 

 abnormality in the presence, anterior to the first inferior tooth, of a 

 distinct alveolus for an extra tooth. It is present only on the right 

 ramus, where it is 9 mm. in advance of the normally placed first tooth. 

 The alveolus measures 11 mm. in anteroposterior diameter by approx- 

 imately 9 mm. transversely. 



DENTITION 



The thirty-two skulls contained in the Museum of History, Science 

 and Art of Los Angeles exhibit a variation in the superior dentition 

 similar to that noted in the University of California series, namely : 



1. Skulls with four teeth on each side of the palate. 



2. Skulls with four teeth on one side of the palate and five teeth 

 on the opposite side. 



3. Skulls with five teeth on each side of the palate. 



The three, possibly four, slender skulls show the following vari- 

 ation : nos. 646 and 643 possess the normal number of five functional 

 teeth on each side of the palate, no. 695 is an example of the second 

 group, in which there are five teeth on one side and only four on the 

 opposite side of the palate, and no. 642 had only four functional teeth 

 on each side of the palate. 



