366 PALAEONTOLOGY OF OHIO. 



rib, which expands to tlie articuhir extremities. In one or two instances 

 the latter are divided by fracture, and moderately concave form of the 

 adjacent surfaces is evident. The diapophyses are of complex form, but 

 the details are concealed by the prevalent thin layer of coal which in- 

 vests them. An inferior prominence runs parallel to the centrum ; out- 

 side of this the process is obscurely trilobate and thickened, not flat- 

 tened, as in the caudal vertebrae of Ptyonius. Several ribs of moderate 

 thickness appear by the side of the diapophyses. Eleven abdominal rods 

 in .005 m. 



Length of a ventrum, .007 m. ; width of articular extremity of do., 

 .004; total width of do., .013; length (antero-posterior) of a diapophysis, 

 .005. 



The second specimen was originally referred by me to the Oestocephalus 

 remex as a posterior portion of its vertebral column, immediately pre- 

 ceding the caudal series. This reference appears to me to be incorrect, 

 although the resemblance between the corresponding parts in the two 

 genera is no doubt considerable, and the alternative of proposing a new 

 genus and species was not at that time advisable. The specimen is pi. 

 21, fig. 2, and is described as follows : It is Nos. 26, 29, Mus. Newberry, 

 a series of dorsal vertebrae that is without head or limbs. The verte- 

 brse are elongate, three of them extending over 2.10 mm. The neural 

 spines are longer than high, and are nearly in contact at their margins ; 

 each is marked by about five obtase vertical ribs. A fractured section of 

 the abdominal dermal spines in place displays at least six superimposed 

 layers of them. 



STEGOCEPHALI. 

 Phlegethontia, Cope. 



Proceedings American Philosophical Society, 1871, 177. 



This is one of the most interesting genera of the present series. It 

 rests chiefly on a single specimen of one species, which is not perfect, 

 but which displays the following characters : Head elongate-triangular; 

 body and tail extremely elongate, the dorsal vertebras without ribs, and 

 the caudals without dilated spines ; no vertebral armature nor limbs. 



As a great portion of the length is presented, and no ventral rods or 

 scales are visible, and as this character is confirmed by a second species, 

 it probably belongs truly to the genus. The pectoral shields are also 

 wanting in the specimen, but as there is a considerable vacuity behind 



