REMAINS OF REPTILES AND FISHES. 73 



attached to them are undoubtedly similar to those of that reputed 

 fish. But on considering that the sculptui'e of the bone surface 

 is exactly like that of the cranial and premaxillary bones, that the 

 teeth of the latter are similar to those of the mandibles, and 

 that the teeth of both exhibit precisely the same Labyrinthodont 

 structure when examined in transverse section, the conclusion 

 that these mandibular fragments really belong to this new La- 

 byrinthodont is quite irresistible. The piscine nature of R. lan- 

 ceiformis is therefore questionable. Certainly the teeth usually 

 so designated belong to this reptile ; and unless other evidence 

 be forthcoming this reputed species of PJiizodus will have to be 

 erased from the list of Carboniferous fishes. 



The two sets of sternal plates are characterized by the same 

 surface ornament which we have found on the other bones ; and 

 though neither of them is perfect, sufiicient is preserved to en- 

 able us, by the aid of both, to form a very good idea of their 

 shape and characters. In the finer and larger specimen all the 

 three plates are present, and by their position exhibit, though 

 considerably displaced, their relation to each other. The pos- 

 terior ends of the two lateral plates lie in juxtaposition, over- 

 lapping the anterior portion of the central plate, and diverging 

 backwards ; a portion only of the posterior margin of the cen- 

 tral plate is exposed. By removing the matrix, however, from 

 the underside in both specimens, the entire form of this plate 

 is developed. The arrangement and general appearance of the 

 three plates are very similar to those of Loxomnia Alhnanni, 

 figured by Prof. Huxley in the paper already referred to ; only 

 the central plate is not so much produced posteriorly, and the 

 lateral ones are much more elongated, agreeing apparently in 

 this latter respect with Archegosaurus, in which Prof. Owen re- 

 marks that the lateral plates " are shaped like beetles' elytra."* 

 Those of Pterojjlax certainly resemble in form elongated elytra ; 

 but, unfortunately, these plates are not perfect ; even in the best 

 preserved specimen only the posterior extremities are entu'e ; 

 they are rounded diagonally, the slope being apparently upwards 

 and outwards. What remains of the most perfect plate measures 



♦"ralxoiLtcln-y." p. ll'.l 



