FROM THE KILKENNY COAL-MEASURES. 3-15 



cited, from the production outwardly of the epiotic cornua, and in 

 tlie belief, as suj^gested by Huxley, that the damaged skull figured 

 by him was imi)erfect anteriorly, I placed Iclithyerpetum next to 

 JVi/rama, The forward position of the orbits and the much more 

 nearly parabolic contour of the present almost perfect specimen 

 show, however, that this relationship is not nearly so close as I had 

 thought. If, however, the figure of the skull of /. hihtrnivum be 

 compared with that of Bothria'ps mistralis'^ Huxley*, from the 

 Ilawkesbury beds of New South Wales, the resemblance is so 

 striking as to leave little or no doubt that we have to do with 

 closely allied forms. It is true, indeed, that the present skull difi'ers 

 by the deeper auditory slits and relatively wider iuterorbital bar. 

 These, however, are comparatively slight points of difference, and 

 we note almost as much diff'erence from Bothn'ceps australis as re- 

 gards cranial contour in the skull of Micropholis Stowi^ Huxley f, 

 from the Karoo system of the Cape. The pustular nature of the 

 cranial sculpture of Microplwlis (Petrophripie) indicates, on the 

 other hand, its generic distinctness from Iclithyerpetum. 



I take it, therefore, that Ichtliyerpetum is a member of that group 

 (" Brachyopina " of Miall) containing Bracliyops^ Bothriceps, and 

 JlicrophoUs ; all of which are characterized by their more or less 

 parabolic skulls and forwardly-placed orbits. The circumstance 

 that Ichthyerpetum has discoidal vertebral centra is very important 

 as helping to determine the affinities of the group. This fact 

 further tends to lend support to the view (provisionally adopted in 

 the British-Museum Catalogue) that the so-called " Brachyopina " 

 are closely allied to Dendrerprtum of the Lower Permian and 

 Carboniferous, which is likewise stated to have discoidal vertebrae, 

 but in which the orbits are placed more posteriorly than in the 

 genera above-named. Since, however, there is a great amount of 

 variation in this respect in the different genera, it does not appear 

 that on this ground alone the so-called "Brachyopina'" should be 

 separated from the Dendrerpetidce. 



One other important matter in connexion with the skull before 

 us remains for consideration. In 1862 Prof. Huxley J described 

 and figured the skeleton of a Labyrinthodont from the Lower Carbo- 

 niferous of Gilmerton, near Edinburgh, under the name of Phulido- 

 yaster pisciformis. Unfortunately only the ventral aspect of this 

 specimen is exposed, so that we have no knowledge of the frontal 

 aspect of the skull, in consequence of which it has been impossible 

 to determine the affinities of the genus. On comparing the inferior 

 surface of the Jarrow skull with Pholi dog aster, a most striking re- 

 semblance is seen to exist between the mandibles of the two speci- 

 mens. The resemblance is, indeed, sufficiently close to render it 

 nearly safe to affirm that Pholidoyaster had a parabolic skull of 

 slightly larger size than the specimen under consideration; although 

 it might, perhaps, be unsafe, on this evidence alone, to say positively 



* Quart. Journ. Geol. Soc. vol. xv. (1859) pi. xxii. fig. 1. 

 t Ifnd. pi. xxi. 



\ Ilrid. vol. xviii. p. 294, pi. xi. fig. 3. 

 Q.J.G. S. iNo. 187. - 2 b 



