MOODIE: MAZON CREEK, ILL., SHALES. 351 
are apparently equal. The cotylus seems to have been far 
posterior and an angle of the mandible projected slightly back 
of the skull. 
There remain only a few indefinite impressions of the 
cervical vertebre. The union of the skull with the vertebral 
column is obscured and lost. Impressions of the dorsal ver- 
tebrze are well preserved. Wax molds made from these im- 
pressions show the structure of the dorsal vertebrz sur- 
prisingly well. The vertebre are long and cylindrical, with 
the median portions slightly constricted by a deep pit on each 
side of the low neural ridge, which takes the form observed 
in Thyrsidium, Molgophis, Phlegethontia, Dolichosoma and 
other genera. The vertebre are strongly amphiccelous and 
the notochord was probably persistent. The sides of the ver- 
tebree are smooth. 
The ribs are all intercentral in position, agreeing in this 
respect with all other Carboniferous Microsauria so far 
studied. The anterior ribs are very broad near the base and 
recall the broadly expanded ribs described by Schwarz for 
Scincosaurus, Ptyonius, Thyrsidium and other genera. Pos- 
teriorly the ribs become slender and cylindrical. They are all 
rather long and distinctly curved, with probably a cartila- 
ginous tip. 
There is preserved a single element of the right side of the 
pectoral girdle. This is, I think, the coracoid, an element 
which has hitherto escaped observation among the American 
Microsauria. It is long, and spatulate at both ends. Its 
median portion was apparently almost cylindrical. Its form 
is not unlike that described by Credner for the coracoid of 
Branchiosaurus, save that the lower end of the branchiosau- 
rian coracoid is acuminate. In the present genus it is spatu- 
late. Its relations with other elements of the pectoral girdle 
have never been satisfactorily determined. 
The fore limbs are both partially preserved. The humerus 
of the right side is complete. It is greatly elongate for a 
microsaurian. The form of the element is not unlike that of 
a lizard. The lower end of the bone is spatulate. Endo- 
chondrium seems to have been well developed. Very little dif- 
ference can be seen between the forms of the arm bones which 
represent the radius and ulna. They are both elongate, with 
constricted median portion and expanded truncate ends. The 
