PYTHONOMORPHS. 403 



The Pythonomorphs, though occasionally found in European deposits, are best 

 known from American specimens, which are abundantly found in the limestone rocks 

 of Kansas and the cretaceous deposits of New Jersey and Alabama. A careful 

 examination of the fragments has shown that the animals were greatly elongate ; the 

 head large, flat, and conical ; the eyes, though placed at the sides of the head, being 

 directed more or less upward ; and the limbs represented by two pairs of broad pad- 

 dles, firmly united with the body. In several particulars these ancient foi-ms resemble 

 the serpents. The teeth were disposed in four rows along the upper jaw, though dif- 

 ferently arranged, for although the palatine and maxillary bones were armed, the pre- 

 maxillary teeth appeared in two rows instead of one. They were used only as organs 

 for seizing the prey, which was swallowed whole, without mastication. The lower 

 jaw had not the bones connecting it with the head movably articulated and allow- 

 ing displacement, though the rami were united in front by the elastic ligament so 

 characteristic of the previous order. The distention of the mouth was provided for, 

 however, by a special structure only represented in a few serpents and in the young 

 of some birds, like the heron. This consisted in the jaws being provided, midway 



Fig. 233. — Jaw of Clidastes ; x, sphenial articulation. 



of their length, with a hinge, the splenial articulation, which enabled the rami to 

 bow out and allow the most bulky prey to gain easy access to the large and spacious 

 gullet. 



By reference to the figure of Clidastes, it will be seen that the pectoral arch con- 

 sisted of only a scapula and coracoid, and that the pelvic arch had no rigid sacrum, 

 and was but loosely united on the middle line below. The ilia were long, and not im- 

 mediately in contact with the vertebral column. The pubic and ischiatic bones were 

 small and free. The pes and manus, and both limbs, were small in proportion to 

 the size of the animal, and of a less robust type than in any other order of marine 

 Reptilia. 



The quadrate bones movably attached to the sides of the skull, the simple articu- 

 lations of the ribs, and the free vertebrae of the sacral region, are points which unite 

 Pythononiorpha with Ophidia and Lacertilia. The general structure of the posterior 

 portion of the lower jaw is like that of lizards, while the chevron bones, protecting 

 the sub-caudal continuation of the aorta, q,re not ophidian. The teeth, being without 

 true roots, are not like those of Lacertilia, nor are they identical with those of Ophidia. 

 It will be seen that the animals require an intermediate position between the 

 previous order and the one succeeding, the Lacertilia. With the other orders, 

 except the Chelonia, which they resemble in having the quadrate bone partly 

 enclosing the auditory meatus, and a few points resembling the Plesiosaurs, they have 

 little or no afiinity. 



The genus Clidastes is represented by about a dozen species once inhabiting the 



