
90 THE FOSSIL REPTILES OF NEW JERSEY. 
which holds through long series of forms, but must be care- 
fully modified for other series, and in some points cannot be 
read at all. 
In Prochonias, as in the modern genus of Brazil, Hydro- 
medusa, the ileum is fastened by a great suture to the shell 
‘above, right on the line of junction of two rib bones. But 
the bones of the front of the carapace, are quite different 
from those of Hydromedusa. In Taphrosphys the structure 
is more powerful. The rib bones are united into one, and 
rise up round the sutural scar, leaving it at the bottom of a 
deep pit. T. molops was a powerful swimmer, and perhaps 
what he lost in mass, was gained in speed. The bony shells 
of both this genus and the last, are sculptured with netted 
grooves (P. sulcatus and P. strenuus) or ribbed lines (P. 
princeps, and T. molops), and they were probably covered 
with a thin skin instead of dermal scales. P. ad inceps was 
large and massive, equalling some of the snapper B 
The more beautifully marked “soft-shelled” eine the — 
Trionyches, are represented by three species. Their posi- 
tion shows that they lived at an earlier period than in Eu- 
rope. The Trionyx of our Miocene (7. lima Cope) was 
large and rough, with narrow sharp ridges. Its remains 
occur with Dolphins and Porpoises, but it may have been 
floated or washed from the mouth of a fresh-water stream 
into such strange company. E 
The Crocodiles of the modern period are kaote by | 
the hollow crowns of their teeth, and one genus of the Creta- 
ceous, Viz., Bottosaurus Agassiz, possesses a similar dentition. 
Most of the Miocene species of both Europe and America - 
possess, on the contrary, solid crowns, composed of closely - 
concentric cones, as we see in Mosasaurus and some other - 
reptiles. Some of them have been on this account mistaken - 
for Mosasauroids, but none of the latter are known above - 
the Cretaceous. In this country the Miocene forms of this — 
. kind are gavials, of even larger size than those of the Cre- 
laceous. They belong to the genus Thecachampsa Cope, of 




