MOODIE: MAZON CREEK, ILL., SHALES. 353 
Genus ERPETOBRACHIUM, new genus. 
The remains on which the discussion of the present genus 
is based are contained in a rounded nodule, with obverse, from 
the Mazon Creek shales, some three and one-half inches in 
diameter. The matrix is the usual reddish ironstone of the 
nodules contained in these beds, and the bones have been 
replaced by kaolin. The parts preserved are the scapula, 
clavicle, portion of the coracoid, the humerus, the ulna and 
radius, all of the right side of the body. 
The generic characters are apparent in the greatly elon- 
gated fore limb, in the exceptionally broad scapula, the long 
radius and ulna, which almost equal the humerus in length 
—a character hitherto unknown among Carboniferous Am- 
phibia. ; 
Erpetobrachium mazonensis new species. 
(Plate 2, fig. 2; plate 8, fig. 3.) 
The scapula of the present form is exceptional in its shape. 
It resembles an asymmetrical pyramid, the anterior side of 
the lower edge of the bone being contracted so that the anterior 
edge is arcuate. Its top is very thin, and possibly terminated 
in a broad cartilage. The lower end is thick and heavy, and 
the articular surface is apparently well formed, though some- 
what obscured. 
The element identified as clavicle is lying on its edge and 
has the proportions of the clavicle of Mazonerpeton costatum. 
The exterior end is somewhat rounded and small. A portion 
of another element, which I suppose to represent the coracoid, 
lies alongside the humerus. Its form is quite obscured. 
The humerus has a remarkably well-formed head. Its 
perfection of formation corresponds well with that of the 
higher reptiles. Its surface can even be divided into an an- 
terior and posterior articulation. It projects posteriorly for 
the distance of one millimeter from the surface of the shaft. 
The shaft immediately below the head is somewhat flattened 
and has an ovoid section. Further on it becomes more flat- 
tened, a part of which is probably due to pressure during 
fossilization. The distal end is somewhat obscured. 
The elements of the fore arm are both preserved, and ar 
approximately equal in size. They are remarkable in tha 
they exceed or at least equal the humerus in length, althougl 
they are not so heavy as that element. They are greatly 
3—Univ. Sci. Bull, Vol. VI, No. 2. 
