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104 Bulletin American Museum of Natural History [Vol. LIX anteriorly, and appears not to reach the orbit, being crowded out by the postfrontal and jugal, a feature undoubtedly related to the forward position of that opening. The frontals are long and narrow. The prefrontals are narrow, but extend forward nearly to the nares lateral to the nasals, which elements have a posterior wedge-shaped extension along the outer sides of the frontals. The premaxillae carry an anterior prolongation of the supraorbital lateral line canals. The lacrymals were wedged in between maxilla and prefrontals, and I cannot be certain whether they reach the nares. Posteriorly they effect a contact with the elongate jugal below the orbits. The maxille are very long, reaching back to about the anterior end of the quadrate-jugals. The marginal teeth are rather thinly spaced. Curiously enough, I have been unable to obtain a satisfactory view of the palate in any one of the rather numerous specimens. Our knowledge of it is gained mainly from specimens laterally crushed which exhibit portions of the palate between the jaw margins. Such evidence as we have tends to show that it was similar, in most respects, to that of Erpetosaurus radiatus. The details of the braincase are not known. The parasphenoid was toothed for much of its extent. The pterygoids articulated movably with the basisphenoid region; they extended far forward, to about the level of the palatine, with interpterygoid vacuities probably of moderate size. There is some evidence that the palatal ramus bore a series of large teeth-a very unusual circumstance-as well as a series of smaller " denticles. " Three large sets of palatal teeth are present, presumably on the ectopterygoid, palatine and prevomer. Those on the ectopterygoid Fig. 10.. Colosteus scutellatus. Type of "Diceratosaurus robustus," X Y. are the smallest; the others, in several instances, show both teeth of a pair functioning at the same time. The contacts between the palatine and ectopterygoid, seen in one instance, seem to be comparable to those in 'Erpetosaurus. The lower jaw is present in several cases but only its outer surface is seen in its entirety. The dentary extends back nearly to the posterior end, in agreement with the posterior reach of the maxillary above. It bears a series of rather stout but thinly spaced marginal teeth, and a
1930] Romer, The Pennsylvanian Tetrapods of Linton, Ohio larger internal series, one near the anterior end being especially large and predicting an opening in the prevomerine region of the palate for its reception. There is a large notch on the outer side of the jaw which allows the passage of the prevomerine thenars, which must have been situated very close to the maxilla. Apparently both splenials were present, as well as the angular and a rather large surangular. 105 Fig. 11. Colosteubs scutellatus. Restoration of skull in dorsal and lateral views About 3 the size of the largest known skull. Some postcranial skeletal material is associated not only with the type but also with several other specimens. The clavicles and interclavicle are considerably expanded ventrally, with a more subdued sculpture than that found on the head. The ventral surface of the body was covered by a regularly arranged series of rhombic scutes of the type usually associated with the labyrinthodonts. These have obscured most
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