OWEN BRACHYOPS LATICEPS. 39 



above-cited figure of the Trematosaurus ; but the true squamosal is 

 always anterior and external to the mastoid in the reptiles in which it is 

 unequivocally present ; and it is restricted to its zygomatic place and 

 functions, not becoming a proper cranial bone until the mammalian 

 type is reached. The precise boundaries of the frontal, 7, and the 

 sutures dividing it from the nasals and prefrontals cannot be traced, 

 the skull being abraded at this part. The postfrontals, 12, have 

 their centre as well marked and prominent as in the mastoids, and 

 extend to those bones from the outer and back parts of the orbits. 

 Traces of the malar, 20, and true squamosal, 27, may be discerned on 

 the left side, extending from the slender maxillary beneath the post- 

 frontal, to the tympanic, 28, beneath the mastoid, 8. The bone here 

 called " postfrontal," is the *'os orbitaleposterius," ^, of Burmeister, 

 and the name " os frontale posterius " is restricted in the above- 

 cited figure of the Trematosaurus to a supplementary bone which is 

 interposed in that Labyrinthodont, as in jthe present, between the 

 bone marked 12, the parietal 7, and frontal n, where it forms the 

 inner half of the back part of the orbit. This bone appears to me 

 to be a dismemberment of an unusually developed postfrontal, and 

 both it and the supernumerary bone, 7*, are remarkable departures 

 from the normal cranial structure, characteristic of some, if not of all 

 of the Labyrinthodont batrachians. The marked departure in the 

 form and proportions of the present cranium from those of the 

 equally well-preserved specimens of European Labyrinthodonts, leads 

 me to the conclusion that the Mangali species indicates a distinct 

 subgenus in that group of Reptiles, and I propose to designate the 

 species so represented by the term ' Brachyops'f laticeps,' indicative 

 of its peculiar proportions. 



Although the abraded and otherwise mutilated state of the skull of 

 the Br achy ops is such as to prevent my giving a more extended ana- 

 tomical description of it, and determining more precisely and satis- 

 factorily the boundaries and homologies of the constituent bones, it 

 nevertheless permits so many characters of the skull of the Labyrin- 

 thodont Batrachia to be determined, as can leave no reasonable doubt 

 of its true nature and affinities ; and thus the results chiefly required 

 by the geologist, in reference to the probable age of the stratum in 

 which this fossil is imbedded, may have been attained. 



DESCRIPTION OF PLATE II. 



Fig. 1. Upper view of the skull of the Brachyops, nat. size. 

 2. Side view of the same, nat. size. 



t From /3pa%vs, short, wxjj/ace ; in reference to the shortness of the facial part 

 of the skull anterior to the orbits. 



