MOODIE: MAZON CREEK, ILL., SHALES. 355 
Genus SPONDYLERPETON, new genus. 
The specimen on which the genus is founded consists of 
nine imperfect vertebrz, from the caudal region, inclosed in 
a brown ironstone nodule from the Mazon Creek shales. 
There have been, up to the present, but two Carboniferous 
genera of the embolomerous Stegocephala described. These 
are Cricotus from Illinois, Kansas and Texas, and Diplospon- 
dylus from Bohemia. Four, possibly five, species have been 
assigned to Cricotus and a single species to Diplospondylus 
(Fritsch, Fauna der Gaskohle, Bd. 2, Tafin 50, 52, 53). It is 
with considerable interest that the writer is able to add yet 
another form to the list of known Embolomeri by the descrip- 
tion of the largest form of the Mazon Creek amphibian fauna. 
The present form exceeds Diplospondylus by twice its size and 
is about two-thirds the size of Cricotus heteroclitus Cope. 
It differs in several important characters from the two 
genera above mentioned, but is for the present to be located 
in the same family, the Cricotidee of the suborder Embolomeri 
and the order Temnospondylia. 
The present form is distinct generically from any form 
which have been described. The generic characters are found 
in the form of the vertebral centrum and in the enlarged inter- 
centra. The present vertebree are twice as high as wide, 
differing thus from Cricotus, in which the centra are practi- 
cally circular. A character which is of great importance is 
the large size of the intercentrum, which almost equals the 
pleurocentrum in size. It is similar to the pleurocentrum in 
structure, except for the attached neurocentrum and chevron. 
The present form differs from Diplospondylus in the greater 
length of the intercentrum and pleurocentrum, in the greater 
size, in the larger proportions of the neurocentrum and the 
greater proportionate size of the intercentra. 
Spondylerpeton spinatum new species. 
(Plate 8, figs. 1 and 2; plate 9, fig. 1.) 
The species is very imperfectly known. Sufficient is present, 
however, to show its wide generic differences from other forms 
of the Cricotoide. These characters are of a phylogenetic 
nature, and indicate the more primitive nature of the present 
form, as we would expect from its geological position. The 
sutures separating the four vertebral elements are clearly 
