MH. K. lvi»i;kki:k on low i;i{ janvs ok I'liocorTonox. 571 



32. On liOAVKK Jaws 0/ riiocoi'ioDoN. By Ji. I^ydkkkkr, Esq., 

 B.A., F.G.S. (Read May 27, 1891.) 



[Plate XXI. J 



The genus Frocojdo'lon M'as established in 1 874 by Sir R. Owen * 

 for the reception of certain large extinct Kangaroos from the Pleis- 

 tocene of Australia — distinguished among other features, by the 

 firmer union of the raandibulai* symphysis in the adult, the shortness 

 and depth of tlie whole mandible, and the relatively small length of 

 the diastema. Moreover, the premolars are characterized by the 

 shortness and thickness of their crowns ; the true molars are long, 

 and usually liave their enamel thrown into a series of vertical folds : 

 while the lower incisors differ from those of living Kangaroos in 

 having cylindroidal crowns. 



Sir K. Owen recognized three species of Procoptodon, viz. P. Goliali, 

 founded u])on afragraent of theupper jaw origin ally described as Jfacro- 

 pus (loliah t ; P. ItapJia, typified by a fragment of an immature man- 

 dible J ; and P. pusio, determined upon the evidence of a somewhat 

 immature and imperfect palate §. It will thus be seen that only the 

 types of P. Goliali and P. pusio are strictly comparable with one 

 another. In the memoir in the Phil. Trans, numerous other 

 imperfect upper and lower jaws were, however, described and 

 figured and referred to the several species. The tj-pe of P. pusio is 

 in the British Museum (IS^o. 39996) ; but there is no record as to 

 what has become of those of the other two species. 



The true type of P. Rapha^ being an immature specimen, is totally 

 unfitted to afford specific characters, and indeed never ought to have 

 been taken as a type. I have, therefore, considered it advisable to 

 regard the imperfect right mandibular ramus figured in the Phil. 

 Trans, for 1874, pi. Ixxvii. (of which there is a cast in the British 

 Museum, Xo. 3il. 3676), as representing this species, although there 

 is no decisive evidence that it is distinct from P. Goliah. Much the 

 same observation will apply to the type of P. Goliah, which likewise 

 affords no well-marked specific characters. 



In part v. of the ' Cat. Foss. Mamm. Brit. Mus.' p. 235, I con- 

 sidered that the tyi)e of P. pusio could not be specifically separated 

 from P. liapha, as represented by the mandible just mentioned ; and 

 the former was accordingly regarded as a synonym of the latter 

 species. I considered, however, that the form described by Sir 11. 

 Owen as Pachysicujon Otiiel •'[ represented another and smaller species 

 of Procoptodon. 



* Phil. Trans, for 1874, p. 788. 



t W'uterhouse's 'Mammalia,' vol. i. (184(i) p. 5*.).— Figured in Phil. Trans, 

 for 1874. pi. Ixxix. Cg. 4. 



+ Phil. Trans, for 1874, pi. Ixxvii. figs. S-U. 

 {^ Ibid. pi. Ixxvii. figs. 2-G. 

 il Ibid. p. 784. 



