TWENTY- THIRD ANNUAL MEETING. 11 o 



Post-fronto-orbitals. — These elements appear as a slender bar running downward 

 and backward, and. in life, evidently also obliquely outward. The union with the 

 frontal above and the jugal below is shown in the figure. The bone is triangular in 

 shape, the jugal suture extending back horizontally about 70 mm. I do not find a 

 differentiation of the two elements, though such may have been the case. 



Temporal arch. — The jugal enters into the posterior inferior portion of the orbit, 

 articulating more than two inches with the jugal above, and by a long, oblique suture, 

 more than four inches in length, with the maxilla below. Just what its relations pos- 

 teriorly are I cannot now say. The bone called "squamosal" I at first confined to 

 the upper j^rocess, but further cleaning makes the supposed suture a doubtful one.* 

 It is possible that what seems a small ossification at the lower end of the quadrate, 

 in front, may be the quadrato-jugal. If this be so. the bar must consist wholly of 

 the -'squamosal" and jugal. The suture distinguishing this " jugal-squamosal" 

 from the quadrate is very distinct, at least in the lower part. It extends from 

 near the lower end, in front, upward and backward, to the posterior surface. Sollasf 

 describes a transverse suture at the anterior part of the arch in Plesiosaurus Cony- 

 beari, whereby '• the jugal, post-orbital and squamosal clearly meet in a T-shaped 

 suture."' There is no evidence whatever of any such suture in the present specimen. 

 Did it exist, the squamosal would necessarily articulate with the maxilla, as weU as 

 the other bones. Prof. Huxley, as quoted by SoUas ( 1. cit.). says that, "contrary to 

 what is usually stated, the post-frontal appears to articulate with a bone, the homo- 

 logue of the squamosal of the crocodile.'" Possibly he is correct, but I believe not. 

 Certainly there is no such arrangement as he figures and positively states in his 

 Comparative Anatomy; upon what evidence I do not know, as more recent authors 

 (Baur, Lydekker) agree in rejecting his views as improbable. There is but a single 

 temporal arch, and it probably, as Baur suggests, represents both the upper and 

 lower arches of crocodilia, Dinosauria, etc. . 



Pterygoids. — The pterygoids unite posteriorly with the lower end of the quadrate, 

 and send off a process, evidently the transverse, back of the middle of the mandibles. 



Premaxillary. — The premaxillaries are large, with pit-like depressions on their 

 outer surface. The median suture is evident; but that separating them from the 

 maxillaries I have traced only a short distance upward and backward. 



Sclerotic plates. — Lying within the orbit are thirteen small, thin, bony plates, the 

 largest about 20 mm. in its greatest diameter, with somewhat crenulated edges. The 

 larger part are lying in position; others are misplaced. 



Mandible. — The lower jaw, from the tip of the symphysis to the hind extremity, 

 measures just twenty inches, of which the teeth occupy thirteen. Its least width, near 

 the middle, is one and three-fourths inches: its greatest width, just back of the teeth, 

 is nearly three inches. The length of the symphysis is two and three-fourths inches. 

 The two dentaries are firmly coossified. traces of the suture being seen at the posterior 

 part only. The ossification is so complete that compression has not affected the 

 symphysial portion, but, instead, has broken the left ramus just back of the sym- 

 physis. The sutures separating the angular, surangular and dentary are, as is seen, 

 very similar in position to those of the crocodile. 



Teeth. — There are sockets in the lower jaws for nineteen or twenty teeth. There 

 is possibly one more on the right than on the left side. Those in the upper jaw 

 seem to be the same in number, though the small posterior ones are so covered by 

 the lower teeth that the number cannot be determined positively. The largest 

 teeth of the upper jaw are the five implanted in the premaxiUary; back of these 



* * This process is s^ld to be distinct in some specimens of Plesiosanrs, and is spoken of as the "supra 

 sciuamosal. or supra temporal." It is probably the triif squamosal, if distinct. Vide Baur, .Tour, of 

 Morph.. III. 473. 



tQuan. .Journ. Geol. Snc, 1881, p. 444. 



