180 MR. T. ATTnKY ON PTEROPLAX COEXFTA. 



surface is convex like that of the postorbitals ; these bones join 

 in front -with the last named, internally with the parietals, and 

 behind vrith the epiotics. The surface-pitting is much less 

 strongly marked on the squamous than on the two bones in front 

 of them. 



The 8upratemporals, the jugaU, and the qiiadrato-jugaU are not 

 visible on the upper surface of either of our specimens. 



The epiotics complete the ring of bones around the sides of the 

 parietals, and form the posterior external angles of the cranium ; 

 these angles are produced backwards, in a conspicuous and re- 

 markable manner, into what have been called horns, whence 

 FteropJax- has received its specific name cornuta. The parts of 

 the skull from which these horns project are thick and strong, 

 standing up in a ridge, which from above the base of the horn 

 passes forwards and then, curving inwards, is merged into the 

 upper surface of the occiput, its external side gradually subsid- 

 ing to the level of other bones. 



The epiotics are narrow bones wedged in, as it were, between 

 the so-called supraoccipitals and the squamous and reaching the 

 parietals ; they also form a portion of the occipital surface, and 

 with it and their horns give attachment to muscles stretching 

 down the neck. 



The so-called supraoccipitals or superior occipitals are rather 

 narrow, elongated transversely, joining each other on the median 

 line, and the epiotics externally, overhang the occipital surface ; 

 their external posterior angles are more or less acute ; below 

 they articulate with the exoccipitals and the quadrates. 



The occipital surface, concave vertically, is much arched fi'om 

 side to side, owing greatly to the epiotic horns, and presents the 

 same slightly overhanging border that wo see in the other two 

 Labyrinthodonts of this district. Three occipital protuberances 

 exist, one at the upper margin, another near to or at the base of 

 the skull, the third, which is small, just below the first. These 

 arc bisected by the median suture. From a little distance on 

 each side of these projections the vertical concavity of the sur- 

 face is divided by a rather rough ridge into an upper and a lower 



