1905.] TtlEUIODONr REPTILE DIADEMODOX. 97 



tooth on the right side shows the anterior serrations, and the 

 second tooth on the right side bears indications of the posterior 

 serrations. At the base of the posterior edge of the onter cusp 

 there is seen in three of the teetli what looks like a very small 

 secondary cusp, but this may be merely a ridge which joins the 

 outer and the inner lai'ge cusps. It will thus be seen that the 

 premolars have crowns very like those of the human bicusps, but 

 differing in having the cusps more marked and with small serrations 

 at least on the outer side. Each tooth that has been displayed 

 has a single cylindrical root. 



All seven molars on the right side, and all except the second on 

 the left, are preserved. The first four are round teeth with flat 

 tops. It is probable that the flattening is largely due to wear, 

 and the enamel seems to have been worn off the tops of at least 

 the first four. In the fifth much of the enamel is worn off, but 

 in the sixth and seventh teeth there is no evidence of wear. In 

 removing the matrix, which is a fine-grained calcareous sandstone, 

 the processes of the enamel were found very apt to adhere to the 

 matrix and to become detached from the dentine, but fortunately 

 almost every feature of the sixth and sev^enth molars is preserved 

 on either one side or the other. 



The sixth molar, when viewed from above, has an almost 

 circular crown, being only very slightly broader transversely than 

 antero-posteriorly. There is a single prominent cusp on the 

 middle of the outer edge, and a second similar but slightly smaller 

 cusp on the middle of the inner edge. Between these two there 

 is a well-developed, slightly concave ridge interrupted in the 

 middle by a slight elevation, and dividing the crown of the tooth 

 into almost equal anterior and posterior portions. The anterior 

 poition, which is moderately flat, slopes down from the median 

 ridge to the anterior edge, which is slightly elevated and supported 

 by three small cusps. These cusps are arranged as follows : — 

 one between the middle of the anterior edge and the large 

 external cusp, but nearer to the middle line ; the other two 

 immediately in front of the large internal cusp. The posterior 

 half of the crown is somewhat similar to the anterior, but rather 

 more concave ; it has the posterior edge supported by a series of 

 small cusps. On the two sides the ariungement is slightly 

 different : on the right side there are four subequal cusps close 

 together ; on the left side one larger cusp takes the place of the 

 centre two. 



The seventh molar is considerably smaller than the sixth, but 

 fairly similar in structure. The posterior part of the crown is 

 narrower than the front part. There are two cusps on the 

 anterior edge, and two, with possibly a small third, on the posterior 

 edge. 



When the lower molars are compared with the upper molai's 

 described by Seeley, it is seen that they fit satisfactorily — the 

 transverse ridge on the lower molars fitting between two upper 

 molars, and the ridge of the upper between two lower molars, 



Proc Zool. Soc— 1905, Vol. I. No. YII. 7 



