MOODIE: MAZON CREEK, ILL., SHALES. 349 
The species Amphibamus thoracatus Moodie has been de- 
seribed in the Proceedings of the U. S. National Museum, 
volume 40, page 431, figure 2, 1911. 
MEASUREMENTS OF THE TYPE OF AMPHIBAMUS THORACATUS MOODIE. 
(Cat. No. 4306, U. S. N. M.) 
mm. 
Length of entire specimen as preserved.......... 60 
Kenothyoreskullmimpressiomheysmiy1iersaleleiele lal 18 
Greatest width of skull impression.............. 15.5 
Long diameter of right orbit..................-- 4 
Transverse diameter of right orbit.............. 3 
Transverse width of interclavicle............... 14 
Long diameter of interclavicle.................- fii 
iLoinee Ghemiaae Or GENMOMs cosoboonropenazoccace 9 
Greatest transverse diameter................... 3 
ILGMYSUN GE ITHACA, poco ogancnooUOOSU Ee coMoGaST 10 
Greatest diameter of humerus.................. 4 
heastidiameter OL AUMeLUS cnc) \.-)-)- lei ele rod 1D 
Ibemedn Gre ieKehing (iN Y)) sc ouocopeoccouscgscon 11 
Length of vertebral centrum................... 2 
Wiadthyof vertebral) centrum... cle. sect ie\er 3 
Genus CEPHALERPETON, new genus. 
This genus is founded on remains of an incomplete in- 
dividual of a relatively large microsaurian from the Mazon 
Creek shales. The genus is most immediately related to the 
family Amphibamidee, of which two species are known. The 
present form differs from these species in many respects, 
notably in size. The skull in the present genus is nearly as 
long as half the entire body of Amphibamus grandiceps, in- 
clusive of the tail. Other structural differences are the aniso- 
dont teeth, the large size and more median position of the 
orbits, and the absence of the posterior tympanic notch in 
Cephalerpeton. The form of the skull recalls that of Melan- 
erpeton and Pelosaurus of Europe, but they are both bran- 
chiosaurians, while the present form, from the structure of the 
vertebree and the long, curved ribs, is an undoubted micro- 
saurian. Nothing like it occurs in the Kilkenny, Ireland, 
fauna described by Huxley, and it is totally different in struc- 
ture from any of the Linton or Cannelton genera, and its like 
is not known among the forms from the continent of Europe. 
It is most nearly approached in certain respects by the various 
species of Erpetosaurus, but from this genus it can be readily 
distinguished by the smooth skull bones, the absence of a 
posterior table to the skull, and the presence of a highly de- 
