16 THE EXTINCT BATRACHIA, REPTILIA SAUROPLEURA DIGITATX, Cope. Proe. Acad. Nat. Sci. Philadelphia, 18GS. 216. This species bad a length of body about equal to that of a fully grown Mamaleo vulgaris of the largest size or of a half-grown Menopoma. Thirteen ribs on one, and several on the other side, are preserved ; where they terminate, probably at the pelvie region, some small or rudimental ribs project from the two or three first caudals. Three ribs and their interspaces extend over five lines. The humerus is broken, but its length can be &early made out to be seven lines ; it has no condyle, and is dilated at both extremities. The ulna and radius are distinct, truncate, hollow, and dilated at the ends. Length of ulna 5.1 lines, distal width 1.8 lines. Carpus not ossified. The fourth toe is considerably longer than the others, the fifth is next and reaches the basal third of the antepenult phalange of the fourth ; the third is very little shorter ; the first is not quite so long as the first two of the third. The bones of the hind limb are not readily distinguished. They are evidently much longer and larger than the anterior ; no part of a foot is preserved. This form is probably allied to Urocordylus. It has relatively much stronger ribs in relation to the vertebra than we have seen in that genus, and there is no evidence of the existence of the vertebra characterizing the latter. The limbs are relatively much stronger than in CEstocephalus, and it lacks the peculiar dermal armature of that genus. cESTOCEPHALUS, Cope. Proceed. Acad. Nat. Sci. Phila., 1868. 218. This genus is represented by a more complete series of remains than any other of the Linton bed. As before remarked, it represents in many respects, the Ophiderpeton of Huxley, and has been alluded to by Dr. Newberry as allied to it. It however, differs markedly in the narrow lanceolate form of the head, with probable accompanying peculiarities of detail, and in the presence of limbs, which have not been found in the Irish genus. The form of the head is somewhat nearer that of Lepterpeton Huxl., but the remarkable form of the spines of the caudal vertebrae so characteristic of the American genus, are not found in Lepterpeton. In this latter respect it is allied to the Urocordylus of Huxley, recently discovered in the Coal Measures in Leinster, Ireland. It differs only in the presence of elongate lizard-like ribs and in the absence of " oat shaped scales" of the lower surfaces. It is a matter of much interest in American Palieontology that this remarkable type should be found to occur in our Coal Measures. It was first announced by Dr. Newberry at the meeting of the American Association for the Advancement of Science for 1867. (See p. 144), as an ally of Urocordylus and Ophiderpeton. The forms discovered by Dr. Newberry have an interesting relation to those of Ireland, such as types of the present period frequently present. The characters of Oestocephalus are: neural and Menial elements of the caudal vertebrae, elongate, distally, dilated and grooved, attached by contracted bases. Ventral aspect defended by a close series of oblique dermal rods on each side, which meet anterior-
