MOODIE: MAZON CREEK, ILL., SHALES. 857 
mentioned. There is no difference, except for the attached 
neurocentrum and chevron, in the form of the intercentrum 
and the pleurocentrum. Its body is pierced by the large 
notochordal canal. 
The condition of the vertebral structures represented by 
the above-described form is so essentially similar to that of 
Cricotus, which has been fully described by Cope, that nothing 
new can be added to the phylogenetic relations of the separate 
pieces of the vertebral column. It is remarkable that such a 
type should be found so low in the geological scale, but it is 
not unexpected, since we must, without doubt, look to the 
early Devonian or late Silurian for the earliest types of the 
Amphibia, which are yet unknown, although they have left 
their footprints in the rocks of the Devonian and Mississippian 
epochs of this country and a single skeleton in the Subcar- 
boniferous of Scotland. That our knowledge of the amphibian 
fauna of the Carboniferous is woefully incomplete is attested 
by the fact that nearly every specimen collected represents 
a type distinct from any hitherto known. Such is eminently 
true of the collection which has just been described. The 
characters on which the genera and species are based are 
apparently ones of value, for they have stood the test of time 
in other groups. 
MEASUREMENTS OF THE TYPE OF SPONDYLERPETON SPINATUM MOODIE. 
(No. 793 (26) and obverse, Yale University Museum.) 
mm. 
LENG UN OE AVA peaouoaeondouo sade poo onooae 60 
jhengthuot pleurocentrunis sys sp cvsii- iets ete) =) 1 = iLL ai55 
Height of pleurocentrum to base of neurocentrum, 20 
benothvor neurocentrumis-). ce cia steels sae eee OS 
Width of neurocentrum at base................. 9 
Width across anterior zygapophysis............. 12 
Width across posterior zygapophysis............ 10 
Menetheotentercentrumesert ccc ierierc racic 10 
IE CANG Oi iro > auoduScUs ado bododaoUoS 10.5 
Heichivotuchevnonanne sek clita) s ae 3 
en obhysok Chevi: OD\ <r .% ois) sasepei or islsner steterstensystecs/s4sKe 18 
Width of notochordal opening.................. 5 
Height of notochordal opening.................. 4.5 
Hershtrot meuralicanelrererrcenrerreiie ckraslstcloisoieas?= 12 
Greatest width of neural canal.................. 6 
