ART. 16 FOSSIL REPTILES FROM MOIS'TAN-A GILMORE 37 



that if completely preserved the extremities of these two Lorns 

 would nearly meet on the median line. Those of the next pair in 

 advance are nearly as large as the hinder pair but point outward 

 more than backward. That there was a third pair is shown by the 

 presence of a small lateral section of the frill, from the side of which 

 a small, stubby process projects outward (pi. 10, j&g. 2). If, as is 

 apparent, this fragmentary part represents the third pair, these 

 processes have their origin considerably forward of the second pair 

 as shown by the smooth, rounded border between them. In S. albert- 

 ensis these processes are relatively shorter, curved, and twinned with 

 the second pair at the base. 



The central part of the posterior border of the interparietal be- 

 tween the posterior pair of processes is thick and rounded and when 

 viewed from above (pi. 10. fig. 2) displays a decided notch on the 

 median line. That large fontanelles were present on either side of 

 a median bar as in S. albertensis is shown by the rapid thinning of 

 the bone on the anterior borders on either side of the middle, and also 

 of the posterior portion of the bar which is preserved. This part of 

 the median bar is broadly rounded transversely on the upper side but 

 flattened beneath. 



The upper and lower surfaces of the frill parts are marked by the 

 usual vascular grooves. The horn-like processes are much flattened 

 above and below and cross sections taken from almost any part 

 would be broadly ovate in cross section. 



Measurements 



Mm. 



Greatest width from tip to tip of second pair of processes 80O 



Greatest lengtli of riglit process of second pair 295 



Greatest width of same at base 93 



Greatest length of shortest process 108 



Greatest width of median notch 57 



Reference of the present specimen to a new species on such frag- 

 mentary material is a procedure that may be open to some question, 

 especially where the specific characters are based upon structures 

 which may be subject to much variation. However, the difference 

 noted in these hornlike processes, except for their much greater 

 size, appear to be comparable to the changes found in the different 

 species of living horned lizards {Phrynosoma) . In the latter case, 

 however, the differences in horn structure are confirmed by other 

 characters such as coloration and scutellation, features that of course 

 are not available to the paleontologist. However, in establishing 

 this species on the available material, fragmentary though it may be, 

 it is with the hope that more complete specimens will disclose other 

 and perhaps more stable characters. 



