from the. Shales of the Northumberland Coal-field. 267 



corresponds verj well in form to the central portion of the 

 fragmentary skull figured in the paper already referred to, by 

 Prof. Huxley ; but in the new form it is less angulated. The 

 frontals, too, appear to be longer, though their anterior extre- 

 mities are broken away ; the post-frontals are arcuated in the 

 same manner, but not to the same degree, forming the inner 

 posterior boundary of the large orbits, and their connexions 

 with the parietals and frontals are similar. The parietals 

 widen backwards ; and the foramen, which is situated in the 

 line of the median suture, where there is an elongated emi- 

 nence, is a little behind their centre, and is slightly lengthened 

 in the antero-posterior direction. In the larger specimen it is 

 one-fourth of an inch in length, in the other it is a little 

 shorter. The occipital margin is concave, the epiotic bones 

 projecting boldly backwards, and each terminating in a slightly 

 arched, pointed, diverging horn or spine, about an inch long. 

 In neither specimen are these horns (which are very similar to 

 the " postero-internal cornua" oi Ke7-ater])eton'^) perfect; but 

 in the smaller individual the upper surface only is wanting. 



The external surface of the cranial shield is strongly sculp- 

 tured in the usual manner observed in Labyrinthodonts ; that 

 is, it is covered with anastomosing ridges separating pits and 

 grooves ; but this peculiar ornament is not equally distributed: 

 it radiates from the centre of the shield, where it is almost 

 obliterated, and is strongest at the margins. Here the pits 

 and grooves are deep and strongly defined. A rather wide 

 rounded groove extends along the outer margin of the frontals, 

 resembling the mucus-grooves of the Labyrinthodonts. 



The larger of these shields is seven inches long, including 

 the posterior horns, and three and three-quarters inches wide. 

 The other is six and one-quarter inches in length, and nearly 

 three inches wide at the broadest part. Prof. Huxley estimates 

 the width of the skull oi Loxomma AUmanm, including the 

 lateral portions, which are entirely wanting in our specimens 

 of Ptei'ojylax cornuta, at ten and three-quarters inches ; and 

 as it appears that the central portion, or that which cor- 

 responds to the cranial shields above described, is about one- 

 third the entire width, we are enabled to form an approximate 

 estimate of the width of the skull of the new form, on the 

 assumption that it had similar lateral cranial expansions. On 

 this basis our new Labyrinthodont must have had a skull 

 eleven and a quarter inches wide at the posterior or widest 

 part ; and, following up Prof. Huxley's estimate, it could not 

 be less than fifteen inches in length. If the body, therefore, 



* Trans, Royal Irish Academy, vol, xxiv., Science, p. 351, pi. 19. 



20* 



