16 
LEA’S DESCRIPTION OF A FOSSIL SAURIAN 
Sandstone of Shropshire.”* This description would almost answer for the vertebrae 
of our Clepsysaurus , and it would seem that this was the prevailing structure of this 
important portion of the frame of the reptiles of that period. 
Having given the facts connected with the condition of the “ New Red Sandstone” 
of this country, so far as ascertained, and stated the views of various geologists on the 
subject, I shall proceed 1o the consideration and description of the saurian hones 
found by Dr. Shelley in Lehigh county, now in the cabinet of the Academy, and I 
acknowledge with thanks the kind assistance of my friend Dr. Leidy. 
In the examination of these interesting remains, we are naturally led first to 
consider their analogies. The epoch in which they were animated, and moved on 
oozy shores, has been remarked for the small amount of animal life which must have 
then prevailed within the area of the sedimentary matter forming this deposit. 
Organic forms of Palaeozoic life had changed, in a measure,—a new phase was 
making its appearance; in fact, a new order of things was in preparation. In the 
carboniferous period the immense growth of vegetable matter which must have 
covered the areas now forming our coal fields, ceased longer to produce these vast 
store houses of carbon. They were finished. The animal life that peopled the 
waters, and the fauna which lived on the soil at that time, no longer existed—all was 
becoming changed. An advance in organization was to be made—mesozoic, or 
secondary life was to assume its sway. We, therefore, naturally find very little in 
previous organisms to establish homologies. In plants the forms had changed; in the 
fishes the heterocercal tail was becoming less oblique; in the reptilia we have only 
the foot-marks, and a few imperfect bones of saurians, to compare with. For 
analogies, therefore, we must rather look to the superior deposits, where reptilian life 
became so prevalent, viz: the Lias, Oolite, etc., there the Teleosaurus, JElodon, etc., 
among the Crocodilidce, and various genera of the Megalosaurinidce , presented species 
of great size and extraordinary abundance, becoming the monarchs of these periods. 
All these present an advance in their organic structure, passing from the bi-concave 
system of the vertebrae to the more perfect concavo-convex system.f 
GENUS CLEPSYSAURUS, Lea. 
The characters of this genus are derived from the form of the vertebrae and the 
teeth. The name is given from the remarkable form of the centrum of the vertebrae, 
which are very much compressed laterally towards the centre. The teeth are 
minutely serrated on the posterior edge, but the serratures are not continued to the 
apex, the superior portion becoming cylindrical. The anterior portion towards the 
base is flattened, presenting at this part a gibbous form. 
* Mono. Permian Fossils, p. 237. f Since the above was in type, I have received from Mr. AV. Struthers a 
large block of this Limestone conglomerate, from Plymouth, 13 miles N. AVest of Philadelphia. I believe it ha? 
not been before observed on the south side of the New lied Sandstone. 
