OWEN NOTOTHEEIUM. 169 



Diprotodon than to any other known genus. The size was apparently that of a 

 large ox ; and the skull agrees with that of the Megatherium, and others of the 

 American tardigrade Edentata (living and extinct), in having a long apophysis 

 descending from the zygomatic arch, as well as in other particulars. However, 

 this process of the zygoma exists in the Diprotodon, and may be detected even in 

 the Kangaroo. Another characteristic of this new quadruped, which may be 

 called Zygomaturus, is the great distance of the zygomatic arch from the tem- 

 poral bone. The breadth of the skull at the widest part — namely, about the 

 centre of the zygoma — is fifteen inches ; the extreme length of the skull is about 

 eighteen inches. In the Diprotodon the skull is, on the other hand, about three 

 feet long by one foot eight inches broad ; so that, while the Diprotodon must have 

 had a facies somewhat like that of a Kangaroo, the facies of the Zygomaturus 

 must have been about as broad and short in proportion as that of a Wombat. The 

 lower jaw of the specimen in the Museum is wanting ; but the formula of denti- 

 tion in the upper jaw is as follows : — 6 incisors, canines, 10 molars. The two 

 front incisors are very long and strong, as in the Kangaroo and Diprotodon. 

 The above dental formula agrees with that of Diprotodon, except that the latter 

 animal had only eight molars in the upper jaw. The Zygomaturus had many 

 points of structure approaching those of the Rhinoceros and Tapir family. For 

 instance, the molars resembled in form those of the Tapirs, while the nasal 

 septum may remind us of the Ehinoceros tichorhinus, a fossil species that 

 formerly inhabited England and other parts of Europe. The strong and very 

 prominent trefoil-shaped arch formed by the extremity of the nasal bones, shows 

 that, if the Zygomaturus did not possess a snout like that of a Tapir, it must, at 

 least, Hke a Ehinoceros, have had a horn (perhaps a double one) on the nose. 

 Without doubt this horn was used for grubbing up the roots of aquatic plants, 

 since, like the pachyderms, to which it bears so close an affinity, in all probability 

 the Zygomaturus passed its Kfe in marshy places. The extraordinary width of 

 the temporal fossae denotes that the animal possessed enormous powers of biting 

 and mastication. 



" This skull belonged to an adult animal, as the molars are considerably 

 ground down. 



" Also, the upper jaw of a young Zygomaturus, as appears by the tips of the 

 molars being perfect. 



" Another portion of an upper jaw, and a humerus, probably of a Zygoma- 

 turus ; base of left ramus of the lower jaw of Diprotodon ; and front incisors of 

 ditto. 



" All the above fossil remains are from King's Creek, Darling Downs, being 

 the same locality whence the entire skull of the Diprotodon was obtained some 

 years ago. Frederick Neville Isaacs, Esq., Gowrie, Darling Downs." 



The notes of Dr. J. D. Macdonald, E.N. (Assist.-Surg. H.M. 

 Herald), are without date, but appear to have been made from actual 

 inspection of the fossil itself, probably on the occasion of the Doctor's 

 visit to Sydney, in 1857 ; they are as follows : — 



" Zygomaturus trilohus (Macleay). 



" The photographic figures of the skull of this remarkable animal, executed 

 by Mr. Wilson, require a few words of explanation, in order that some at least 

 of the many queries which will natiiraUy arise in the mind of an anatomist 

 inspecting them, without the means of consulting the original, may be as it were 

 anticipated and answered. 



" First, then, the granular appearance of the surface is due to the adhesion of 

 particles of grit and alluvial matter, which had not been removed ia consequence 

 of the extreme brittleness of the bone beneath. 



" The tables of the skull are of great thickness, and thrown apart by large 

 ceUidar cavities, lined with a compact osseous tissue. The frontal sinuses espe- 

 cially are of enormous size, divided by a thin vertical septum, and giving rise to 

 the angular fulness of the antero-lateral part of the forehead. A small piece of 

 the outer table having been broken away on the right side of the occiput, an 



