Both scapulæ are preserved in their entire form. They are quite different from those of any other genus, being broadly crescentic with a posterior concavity and an anterior protuberance. The anterior surface of both scapulæ is obscured. Vascular foramina occur near the base of both scapulæ; there being three of them in the right scapula, arranged in the form of an isosceles triangle. The morphology of these foramina is uncertain. They have never been observed among the Carboniferous Amphibia, and, so far as I am aware, they are entirely unknown among higher vertebrates. The temnospondylous Amphibia of the Carboniferous and Permian possess, in the coössified scapula-coracoid, three foramina, very similar to the ones in the present form, but they are confined to the coracoidal region and, in the Branchiosauria, as identified by Credner, the coracoid is a free element, although I have never been sure of its identity among American forms. Williston has called these foramina the glenoid, the supraglenoid, and the supracoracoid foramina (Journal Geology, XVII, No. 7). They are not, however, to be correlated with the three foramina above mentioned, since in the Temnospondylia the foramina belong with the coracoid and not with the scapula. The condition of the Temnospondylia occurs in the bony fish _Xiphactinus audax_ Leidy, and an analogous condition obtains in the reptiles, as in the Mosasaurs and Dinosaurs. [Illustration: Fig. 14_a_. Skeleton of _Mazonerpeton longicaudatum_ Moodie. _c_, carpus; _cl_, clavicle; _cr_, caudal ribs; _cv_, caudal vertebræ; _h_, humerus; _f_, femur; _or_, orbit; _r_, radius; _sp_, sclerotic plates; _sc_, scapula; _u_, ulna: _vs_, ventral scutellæ. From Mazon Creek. Original in Yale University Museum.] Near the outer edge of the right scapula there is a large fragment preserved, which, I think, must be the misplaced clavicle. It is obscurely triangular or, more exactly, spatulate. The interclavicle is represented by fragments only, and seems to have had a narrow form. The humeri recall those of _Micrerpeton_. They are somewhat elongate and apparently cylindrical in their normal condition, although somewhat flattened in the fossil. The shaft is considerably constricted at the middle and the ends are expanded, in which expansion the lower end exceeds. The ends are abruptly truncate, indicating a small amount of endochondral ossification or its entire absence. The mesopodial elements, unlike what is described for _Cephalerpeton_, are quite dissimilar in form, recalling the condition in _Mesosaurus brasiliensis_ McGregor. The larger element is, apparently, the ulna. It has the lower end greatly expanded and the shaft is curved outward, resembling very much a reptilian ulna. The radius is much smaller than the ulna, lacks the lower expansion, and is shorter by 1 mm.