458 
PEOPESSOE owm ON THE DICTNODONT EEPTILIA. 
tulous trenchant border of the premaxillaries, n. The back part of the maxillary is con- 
tinued beneath the orbit in a pointed form, articulating by a strong, oblique and exten- 
sive suture with the malar (fig. 1 , 25 ), by which and the lacrymal the maxillary is removed 
from the orbital border itself. 
The lacrymal (73), forming the middle of the fore part of the orbit, extends upon the 
face apparently to the nostril. The malar curving back along the lower part of the 
orbit, the border of which it there forms, bifurcates behind to connect itself with the 
postfrontal (figs. 2 & 4, 12 ) above and with the squamosal (fig. 1, 27 ) behind; but their 
limitary sutures I cannot satisfactorily make out. There is no other bony bridge over- 
spanning the temporal fossa except the normal malo-squamosal zygomatic arch. The 
squamosal combines with the mastoid in affording the articular sutural surface to the 
upper end of the tympanic. 
The squamosal (fig. 1, 27 ) is compressed, of 8 lines in vertical extent, by 2 in trans- 
verse ; and increases vertically as it passes backward. The tympanic pedicle is of great 
length, broad and compressed from before backward at its upper part, becoming 
narrower as it descends, but gaining in thickness to where it receives the broad abut- 
ment of the paroccipital ; below which it slightly expands in every direction to form 
the convex articular surface for the mandible. The tympanic pedicle is fixed immove- 
ably, and by its size and connexions forms an unusually strong ‘point d’appui’ for the 
vigorous actions of the lower jaw. It consists of two bones, united by a broad over- 
lapping squamous suture. The upper portion includes the mastoid and squamosal 
elements ; the latter extends to near the articular condyle, along the fore part of the 
pedicle; the lower portion, or tympanic proper ( 23 ), forms the lower half of the back 
part of the pedicle, and expands below to form the joint. 
The mandible of PtychognatJms (fig. 1, 30-32) resembles that of the Chelonia in its 
edentulous condition, general proportions, and comparative simplicity of structure, and 
that of the Crocodilia in the vacuity left between the dentary (32), angular (31), and sm- 
angular (30) elements ; but it is peculiar and ptychognathic in the sudden vertical expanse 
and upward curve of its symphysial end (32'), the vertical diameter here being three times 
that of the articular end. I cannot distinguish an articular from a smungular element : 
the suture between this and the angular extends near and runs parallel with the upper 
border of the surangular to the vacuity, towards which it bends. No coronoid process 
is developed, nor is there any coronoid or complementary ossicle as in modern Lizards, 
Chelonians, and Crocodiles. The splenial element (fig. 5 , 29) extends far back, as in Che- 
Imia. The dentary elements, confiuent at the symphysis, are deeply notched at their 
naiTow hinder part, the upper projection being the longest. A horizontal ridge extends 
from the upper part of the notch forward as far as the depression, lodging the end of the 
canine tusk when the mouth is shut. The vacuity is situated halfway between the two 
ends of the mandibular ramus, not in the posterior third as in the Crocodile. The sym- 
physis is broad as well as high, and the rami meet there so as to form, below, an arch 
or curve, concave backward, fig. 5, s. The fore part of the symphysis is convex both ver- 
