380 PALEONTOLOGY OF OHIO. 



Length of type from anterior edge of pectoral shields, 0.085 m. ; length 

 of median pectoral plate, 0.006 ; width of neural and haemal spines at 

 first caudal vertebrae, .0046; do. at middle of tail, .004. 



Oestocephalus, Cope. 



Proceed. Acad. Nat. Sci., Philada., 1868, p, 218 ; Transac. Amer. Philos. Soc, XIV., 



p. 16, 

 Sauropleura, pt. ; Proceed. Acad. Nat. Sci., Philada., 1868, p. 217; Proceed. Amer. 



Philos. Soc, 1871, p. 41. 



Another genus resembling in its fan-like haemal and neural spines of 

 the tail the European form Urocordylus, and differing from it as Ptyonius 

 does, i. e., in the rod-like abdominal scales. Its form is long and snake- 

 like, and it thus resembles Ophiderpeton, Huxl. But in the latter there 

 are no limbs, and the cranium is very difierently constructed ; in Oesto- 

 cephalus it is much as in Ptyonius and Lepterpeton. The characters then 

 are as follows : 



Form slender and snake-like ; caudal vertebrae with dilated and sculp- 

 tured neural and haemal spines. Cranium lanceolate. Teeth numerous, 

 of nearly equal size. No pectoral shields abdomen protected by very 

 numerous bristle-like rods, which converge forward ; scales none. A pair 

 of weak posterior limbs ; branchihyal bones present. 



In the only well-preserved species the cephalic bones exhibit no sculp- 

 ture from the parietal region forward. The angles of the mandibles are 

 prolonged backward, as in Apateon and the Anura, and the well-developed 

 ribs commence but a short distance behind the head. The vertebrae are 

 slender and furnished with well-developed diapophyses. The neural 

 spines of the dorsal vertebrae in 0. remex are flattened and antero-poste- 

 riorly expanded and weakly grooved to their superior margin. 



The character which separates this genus from Ptyonius is the absence 

 of the three usual pectoral shields. In two specimens the pectoral re- 

 gion is presented, and no trace of the shield appears ; on the contrary, 

 the ventral armature of brigtles or rods extends to the head. 



A pair of symmetrical bones, whose impressions are seen posterior to 

 the occipital bone, I once thought might belong to rudimental limbs. 

 They, however, appear to be the elements of the second or third branchial 

 haemal-arch ; the first, or haemal, followed by a second element, which is 

 probably the inferior pleural segment of the arch. A third piece follows, 

 which is the superior pleural element of the same. The other branchial 

 arches are lost,^but some impressions are visible. 



