146 SIR RICHARD OWEN ON THE SKULL AND DENTITION 
5. On the Sxutt and Dentrtion of a Trrasstc Mammat (Tritylodon * 
longevus, Owen) from Sourn Arrica. By Sir Ricnarp Owen, 
K.C.B., F.R.S., F.G.S., &. (Read November 21, 1883.) 
[Puate VI.] 
A coutuectrion of fossils from the Trias of Thaba-chou, Basuto-land, 
submitted to me by Dr. Exton of Bloemfontein, Cape of Good Hope, 
included the subject of the present paper. It was associated with 
remains of some of the Reptilian genera (Kisticephalus, Batracho- 
saurus, e. g.) described in my ‘ Catalogue of the Fossil Reptilia of 
South Africa in the British Museum ’ +. 
It is a skull with mammalian characters, jackal the hinder 
cranial end and the mandible, but retaining with the upper jaw its 
dentition, though many of the teeth are more or less mutilated. 
This dentition consists of incisors and molars, with a diastema of 
the relative extent shown in many Rodents and some Marsupials. 
The subjoined figures (Pl. VI. figs. 1-4), being of the natural size, 
dispense with notes of admeasurements. 
The matrix adhering to this fossil is identical in colour, density, 
and composition, with that attached to the Labyrinthodont and other 
Reptilian remains therewith associated: the degree of petrifaction 
and the specific gravity of the mammalian fossil are the same. No 
Tertiary deposits or any recent petrifying formation, inducing such 
mineral change in bone and contiguous bed, exist in the locality 
whence this skull and the associated organic remains were ob- 
tained. 
In the preserved portion of the cranium (PI. VI. figs. 1, 2, 3) sutural 
tracts are recognizable: these determine the pair of parietal bones 
by the portions of them, 7, 7, which contribute to the calvarium ; 
they meet above the upper mid line, and there develope a crest 
which has undergone abrasion. This part indicates an anchylosis 
of the parietals into a single bone. A short anterior divarication 
bounds a small vacuity exposing matrix which has filled the cerebral 
cavity ; which vacuity is. completed anteriorly by a similar divari- 
cation of the mid and hind angles of the frontal bones, the mid 
suture of which is unobliterated. The above vacuity, v, if natural, 
represents a fontanelle, or it may be interpreted as a ‘ pineal’ 
or parietal foramen; it may, however, be due to posthumous 
injury. 
Each frontal (fig. 1, 11, 11) expands and forms the upper border 
of the orbit, 0, of its side, which border is obtuse. The upper 
surface of the frontal, at a short distance mesiad of the orbit, is 
traversed by a rather shallow longitudinal groove. To the antero- 
lateral angle of each frontal is articulated a lacrymal bone (fig. 1, 73) 
of moderate size, encroaching a short way upon the face, perforated 
* roeis, three, TiAos, knob, édods, tooth. 
tT 4to, 1876, pp. 88, pls. i-lxx. 
