360 



LIEUT. R. BROOM OX 



The following are the other principal measurements : — 



Measurement between the canines, 40 mm. to 48 nun. 

 Interorbital width, 25 mm. 



Measurement across the nasal bosses> 44 mm. to 52 mm. 

 Interorbital measurement, 36 mm. to 38 mm. 

 Intertemporal measurement, 28 mm-, to -36 mm. 



The premaxilla is relatively narrow in front. It has the 

 usual pair of palatal ridge'* seen in most Anomodonts. It forms 

 much the larger part of the hird palate-, and meeting the palatine 

 behind shuts out the maxilla from the margin of the posterior 

 nares. In the middle line the prem;\xilla meets the prevomer, 

 as shown in tlie figure. 



Text-fio-ute 4. 



Antericv p:ilat;\l region of "tropiifosfoma mirroti'emd (Seeley). J- uat. size. 



Showing- the lelatioils of tlie palatal elements and tooth-soekets behii-.d the canines. 



B.M., R 860. 



For lettering see text-fig. 1, p. 356. 



The maxilla is very siuiilnr to that of Bicj/uodon except for the 

 presence of molar teeth. With the premaxilla it forms the lower 

 border of the nostril, meeting the septomaxilla. Its upper 

 border articulates with the lacrimal, which completely separates 

 it from the nasal. 



In nearly all the specimens of Tropidostoma microtrema there 

 are seen some molar teeth or tooth -sockets. In voung specimens, 

 which are about half the adult size, there are four molars, of 

 which the first is the largest, and they decrease in size to the 

 fourth. The four molai's measui-e 10 mm. Only one specimen 

 shows the crowns. These resemble closely the molars of 

 Pristerodon. but those of Tropidostoma are rather stouter and 

 the denticulation slightly coarser. In the 1st molar there are 



