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124 Bulletin American Museum of Natural History [Vol. LIX of the palate is not better known, as the controlling factor of width in this regiol is somewhat uncertain. A specimen (6917) figured by both Cope and Moodie as one of Sauropleura scutellata gives some information as to the postcranial structure. (An unnumbered specimen in the National Museum is similar.) That this specimen pertains to M. huxleyi is demonstrated by the identity in pattern of the posterior portion of the table of the skull, the only portion of the cranium preserved. The dermal shoulder girdle, Fig. 21. Macrerpeton huxleyi. Restoration of skull. as may be seen from the figures of Moodie and Cope, includes broad clavicles and interclavicle; there are no cleithra or post-temporals visible. The flattened ventral surface of the dermal elements suggests an early secondary aquatic habitus in this group. The sculpturing consists of radiating lines, which would not be expected from the punctate pattern of the posterior portion of the skull. This radiate arrangement, as may be seen, is identical with that of Sauropleura pauciradiata, as figured by Cope and Moodie.
1930] Romer, The Pennsylvanian Tetrapods of Linton, Ohio 125 The ventral scales on development are, as usual, rhombic in surface view. The thickened posterior margin, however, has indentations facing posteriorly (usually three in number) in contrast with the smooth margin of the "normal" labyrinthodont scale Ȯf the anterior limb elements, the radius and ulna, 10 mm. in length, may be seen in the figures. The humerus is partially obscured by the squamation. It is about 15 mm. long, and of about the proportions of this element in Trimerorachis. The vertebra and ribs are almost completely concealed by the squamation. The ribs were about 30 mm. in length, and, as preserved, had but little curvature. They are spaced approximately 8 mm. apart. The skull fragment accompanying these remains has a width across the table of about 85 mm. and an estimated skull length of 23 cm. The figures given above suggest that Macrerpeton paralleled secondarily aquatic forms among the Rachitomi and Stereospondyli in many respects. The skull was exceedingly large in proportion to the body. If about 30 presacral vertebrae were present (the primitive number may have been close to this), the trunk would have measured 24 cm. in length in this specimen, only slightly more than the head. The anterior limb, less the manus, was little more than a tenth the length of the skull, making terrestial locomotion out of the question. Ichthyacanthus ohioensis was described by Cope from a vertebral column, with ribs and hind limb material present. The specimen was never figured, and apparently it never was placed in any permanent collection, for Cope in 1885 stated that the specimen was not then available. Moodie apparently did not see it (since in 1916 he merely quotes Cope's description), and repeated search in the American Museum and Columbia University, where all other early types from Linton are preserved, has failed to uncover it. It is perhaps best to regard the species as a nomen nudum, since Cope's usually somewhat hasty and superficial treatment of other Linton specimens prevents placing too much confidence in the details of his descriptions, in the absence of the possibility of verification. However, it is interesting to consider the possibility that this lost specimen was the posterior portion of the skeleton of Macrerpeton. His description of the inclined caudal neural and haemal arches suggests a typical labyrinthodont condition (cf. Spondylerpeton, as described below), and his statement that the tarsus was ossified also suggests this group. He states that the dorsal vertebrae average 4.7 mm. in length, making the limbs quite large for the column. It is quite possible, however, that the "ten dorsal vertebra" mentioned by Cope really consisted of five centra and five intercentra, making the length of a single segment 9.4 mm., or slightly more than in
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