12 CAI.IKoliXlA ACADK.AIY ( H' SCIKXCKS 



of tlie bar. Even on tlie most coiuplete spcriuuMis (I'ls. in and iv) it has been 

 impossible to determine certainly whether a prosquamosal is present or not, as 

 the character of the bone is sucli that the sntnres immediately above the 

 quadrate are very difficult to determine. On what is taken to be the quadrate 

 in a frafiinent of the temporal retiion of the type of TliakiftosaKrii.-^ (1*1. ii, fig. 4) 

 there rests a downwardly' projecting arm which appears to be a part of an ele- 

 ment that belonged to the lower side of the upper temporal bar. Evidentlv it 

 extended down the outer wing of tlie (|uadrate, almost if not quite to the 

 quadratojugal. The inner side of this bone, as also of that resting on the 

 summit of the (juadrate, is weathered away and it is not impossible that they 

 were originally connected. If united, the squamosal must have had a form 

 somewhat similar to tliat of SjiliciKxhui. If separated, the lower (dement is 

 apparently a discrete prosquamosal. 



Quadrate, Suspensoriam. — The (jnadrate is well shown in position in one 

 specimen (PI. in, fig. 2) and macerated out, though associated with the posterior 

 end of the mandible and the cranium, in another (PI. ii, tigs. 2a and 2b). It is of 

 distinctly rhynchocephalian ty{)e, though approaching the laccrtilian form in 

 the development of a stronger posterior hook and a broad exterior wing. While 

 the posterior side of the distal end is rounded upward the anterior side is dis- 

 tinctly flattened as if from contact with a quadratojugal. The presence of a 

 high extero-laternl wing seems to precdude the possibility of there having been a 

 fenestra between the quadrate and (luadratojugal, as in the typical Rhynchoceph- 

 alia, thovigh there may have been a small opening near the distal end. 



The relation of the quadrate to the temporal bones is such that it must have 

 been immoval)le, in contrast to the general relations in the Squamata. 



Orhitdl H('!/iini. — Tlu' specinu'ns of 'rhdldftdsaiiriis show portions of large 

 sclerotic plaf(.'< in the orbits. They are similar in form to those seen, in the 

 Mosasaurs. In at least one instance a plate is deeply grooved on the margin, as 

 occurs in forms in which the sclerotic ring is particularly heav}' and strong. 



In the boundaries of the upper side of the orbit the prefrontal and post- 

 fronto-orbital come so close together that the frontal hardly appears on the rim 

 of the orbit. The posterior boundary is formed by the heavy ascending process 

 of the jngal, and a single uj)per element evidently representing both the post- 

 frontal and the postorbital. No evidence has been obtainecl which would tend 

 to indicate the existence of a separate jiostfrontal resting al)ove this bone. The 

 apparent contact of the squamosal with the frontal might be interpreted to mean 

 that a greatly reduced postfrontal is fusecl Avith the anterior arm of the squa- 

 mosal, but until we have more definite proof of this it can be considered only as 

 a mere possibility. 



