MOODIE: MAZON CREEK, ILL., SHALES. 325 
forms occurring elsewhere in the Carboniferous or later ages. 
It has been the writer’s good fortune during the past five 
years to examine all of the specimens of Carboniferous air- 
breathing vertebrates in North America, with the exception 
of Sir William Dawson’s collection at McGill University. The 
European forms, as they have been described from time to 
time, are, unfortunately, known to him only through the lit- 
erature, with the exception of a small collection of Branchio- 
sauria recently received in exchange from Dr..Hermann Cred- 
ner. It is hoped that in the near future this may be supple- 
mented by actual observation, and until that time it can not be 
positively asserted that the forms described below are unlike 
those already known, but, so far as his knowledge goes, the 
writer is confident that they are new to science. The char- 
acters used for generic distinctions are such that even the 
most superficial observations must reveal. They are struc- 
tural ones, and are those which are used by many eminent 
vertebrate paleontologists at the present time. Unfortunately, 
we know so little about the development of the class Amphibia 
that we can not always be sure that our characters are phylo- 
genetic, as they must be to mean anything. So that until some 
idea of phylogeny is obtained, structural characters must be 
used which seem to the describer to be of generic significance. 
The Amphibia so far discovered in the Mazon Creek shales, 
including those described in this paper, are: 
Amphibamus grandiceps Cope, 1865. 
Amphibamus thoracatus Moodie, 1911. 
Micrerpeton caudatum Moodie, 1909. 
Eumicrerpeton parvum Moodie, 1910. 
Mazonerpeton longicaudatum Moodie. 
Mazonerpeton costatum Moodie. 
Cephalerpeton ventriarmatum Moodie. 
Erpetobrachium mazonensis Moodie. 
Spondylerpeton spinatum Moodie. 
Erierpeton branchialis Moodie. 
These ten species are distributed among eight genera, five 
families, and four orders, thus showing the amphibian fauna 
of Mazon Creek to be a diverse one. The arrangement of the 
species into groups is given below. 
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