THE AMERICAN COAL MEASURES BRANCHIOSAURID^. 6l 



Genus MAZONERPETON Moodie. 

 MooDiE, Kans. Univ. Sci. Bull., vol. vi, No. 2, p. 336, 1912. 



Type : M. longicaudatum Moodie. 



The genus is distinguished from other known branchiosaurian genera by the 

 great length of the dorsal region, the elongate tail (plate 5, fig. 2), with its well- 

 developed caudal ribs, the reduction of the tympanic notch, the broad nature of the 

 scapula, the elongate interclavicle, and the slender ilium. The niomber of dorsal 

 vertebrae is identical with that of Branchiosaurus of Saxony. 



Mazonerpeton longicaudatum Moodie. 

 Kans. Univ. Sci. Bull., VI, No. 2, p. 337, pi. 3, figs. 1-2; pi. 7, fig. 3; pi. lo. 1912. " 



Type: Specimen No. 795 (1234), Yale University Museum. 



Horizon and locaUty : Mazon Creek shales, near Morris, Illinois. (Plate 3, figs. 

 5 and 6.) 



The remains consist of the following elements : an incomplete skull ; nearly the 

 entire vertebral column, consisting of cervical, dorsal, sacral, and caudal vertebras, 

 36 in nvmiber; several ribs preserved on each side of the vertebral column; a portion 

 of the ventral armature ; the scapulae ; a clavicle ; the interclavicle ; both humeri ; the 

 radius and ulna of one side and the ulna of the other; portions of both hands; the 

 ilium of the right side; both femora, and a partial impression of the left tibia. 



The skull is, vmfortunately, very poorly preserved. Enough remains, however, 

 to determine the essential characters. The skull bones, unlike any other American 

 branchiosaurian, have an ornamentation consisting of sharp pits and elevations 

 which in places have a quincuncial arrangement and in others take the form of defi- 

 nite lines of pits or tubercles similar to the condition found in many of the Micro- 

 sauria. The orbits are large and are situated back of the median transverse line of 

 the skull. They are almost circular in form and contain 6 elongated sclerotic plates 

 very closely arranged around the borders of the right orbit. The plates are twice 

 as long as wide. The interorbital width is 1.25 times the transverse diameter of the 

 orbit. 



Not many of the sutures of the skull are discernible. Portions of the frontals, 

 the nasals, the prefrontals, the parietals, and the supratemporals can be identified. 

 Their arrangement is shown in figtire 14c. There is a decided posterior table to the 

 skull, with truncate posterior border. The tympanic notch is shallow, with its 

 outer border not so well protected as in Branchiosaurus. 



The cervical vertebrae are incomplete, but their number was 4 or 5, as in Mic- 

 rerpelon. The structure of the dorsal vertebrae is also uncertain, although the shape 

 can be discerned. The vertebrae are short and thick, very imlike the long, cyUn- 

 drical vertebrae of Cephalerpeton. The heavy transverse process is quite evident on 

 the best preserved vertebrae. This process recalls that described by Credner for the 

 Saxony Branchiosauria. Several of the vertebrae show the articulation of the ribs 

 with this process. The ribs of the caudal region recall very strongly those of Branch- 

 iosaurus. They are quite heavy in the anterior caudal region and then diminish 

 rather rapidly to the point where the tail is broken and lost. 



