MKIMMA.M TlIK Til A I,ATT< ISA T i; I A 15 



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Opposite iiiar.iiiii of tlic plate supports a lii^li. tliin, ti-iaii^ular wiiii;- standing 

 almost parallel witli the tootli-heariiig sui-faee. Tlie surfaee of this wiiig is marked 

 on one side hv I'adiating sculpture sotnewliat like that of the maxillary, except- 

 ing that it is larg(dy in ndief. The at'ute end of the wing is drawn out to a ver}' 

 thin edge. The hroad end is eonsiderahly thicker and shows a deep groove 

 wliere it was prohahly in contact with the (piadrate. 



The j)f<T)/i/iiitl fctili are in four rows with alveoli for a hfth. I'nfortunately 

 the crowns of nearly all wei-e hroken oi- weatliercMl off and only the w^ell preserved 

 fangs remain. The tei'th are all set in distinct pits and are inclined sliarply 

 toward the thi(d<ene(| enil of the hone. 



Considering that the palatine is <'dentulous and the vomerine teeth have 

 speciali/,e(l toward the low, hr^ad type present only in a single row on eacdi side, 

 it is rather remarkahle that the pterygoid teeth should he so numerous and 

 evidentlv of the recurveil. conical tyj)e. There is, however, no apparent escape 

 from the conclusion that sucdi is the case. Apparently the vomerine teeth 

 serveil largelv as crushers, while the iiterygoid teeth assisted deglutition. The 

 type of pterygoid represente(l here does not correspond exactly to an}^ that has 

 so far come to the writer's notice, hut is not far removed from the type seen in 

 some Kliynchocephalians. 



In one specimen of T. slidstensis (PI. iii, fig. '2., Kp) thei'c appears to he a frag- 

 ment of an epipterygoiil in its natural position al,)o\'e the pterygoid. No ecto- 

 ptei'ygoid has heen recognized. 



Mainlihie. — (I'Is. r, iii and iv). Though no single specimen shows the whole 

 of the lower jaw. overlap])ing portions of several exhibit the whole structure of 

 both the iniiei- and outer sides. The jaw is characterized hy the sculpturing of 

 the dentary, as shown in the type of Tlialaito-^ditrKs, hy the length of the angular, 

 and by the promincMU'c of the coronoid pr<K"ess. 



The deiifary does not appear to form the lower burdei- of the outer side of 

 the jaw exce{)ting along the most anterior portion, owing to the extreme forward 

 extension of the anguliir. The connection of the ranu at the symphysis was 

 loose and they have fallen awav from each othei' in all of the specimens examined. 



In Thaldtfdsdiirtis the ti'cth u])on the dentary extend back almost to the 

 extreme jxjsterior end of that bone, where they are low down on the inner side of 

 the jaw. Th(\\' are either set in depi'essions or appear to be fuseil to the jaw. 



The extreme posterior end of the jaw is forme(l by the articular, which 

 extends forward to be covered anteriorly by the splenial. The supra-angular is 

 large and makes up the greater part of the posterior half of the jaw. The 

 angular also forms a considerable part of the outer side of the jaw and ranges 

 forward well toward the antei'ioi- end of the ramus. A large splenial covers 



