68 
Amphibia — Archcegosaurus , etc. 
the dentine ; the upper surface of the skull being pitted ; the 
supra-occipitals ridged ; a ring of hones is usually developed in 
the sclerotic ; the ventral surface of the body is always covered 
with scutes. This family is evidently the most primitive one 
of the entire group. 
A B 
Fig. 90 .—Cricotus heteroclitus (Cope).— Ventral scutes (A), and frontal aspect of the 
cranium (B) ; from the reputed Permian of Texas. ( After Cope.) 
Wall-case, The genus Archa>gosaurus, represented by A. Decheni (Gold- 
No. ll. fuss), from the Lower Permian “ Rothliegendes” of Saarbriick, 
Rhenish Prussia, is particularly well represented in the Col- 
lection by a remarkably good series of examples. This genus 
is confined to the Permian formation, and may be taken as 
the type of the family. The skull is nearly twice as long as 
it is broad, with elongate-oval orbits, and situated very-far 
back; length of skull 11 inches. 
Platyoposaurus is closely allied in cranial characters to 
Archcegosaurus , but the infoldings of the teeth are sinuous 
instead of straight, and the orbits are more rounded. This 
genus is found in the Permian (Zeclistein) of Russia. 
