Te, 
Geological Society. 61 
PROCEEDINGS OF LEARNED SOCIETIES. 
GEOLOGICAL SOCIETY. 
November 21, 1883.—J. W. Hulke, Esq., F.R.S., 
President, in the Chair. 
The following communications were read :— 
1, “ On the Skull and Dentition of a Triassic Mammal (7’ritylodon 
longevus, Ow.) from South Africa.” By Prof. Owen, C.B., F.R.S., 
F.G.S. 
The specimen described in this paper formed part of a collection con- 
taining remains of some of the known South-African Triassic Reptilian 
genera, and agreed with them in its mode of fossilization. It was 
submitted to the author by Dr. Exton, of Bloemfontein. The spe- 
cimen is a nearly entire skull, wanting only the hinder part, and it 
measures about 3? inches in length, from the broken end of the 
parietal crest to the point of the united premaxillaries. The upper 
surface shows the anchylosed calvarial portions of the parietals, 
and the frontal bones divided by a suture ; the contiguous angles of 
these four bones are cut off, so as to leave an aperture, occupied by 
matrix, which may be a fontanelle, or a pineal or parietal foramen. 
The frontals form the upper borders of the orbits, which are bounded 
in front by the lacrymal and malar bones, and were not completed 
behind by bone. ach frontal is narrowed to a point at the 
suture between the nasal and maxillary. The nasals are narrow, 
but widen in front to form the upper border of the exterior nostril, 
which is terminal, and is completed by the premaxillaries. The 
maxillaries are widened posteriorly, then constricted, and again 
widened before their junction with the intermaxillaries. 
The teeth include a pair of large round incisors, broken off close 
to the sockets, and showing a large pulp-cavity, surrounded by 
a complete ring of dentine, which is covered by a thin coat of 
enamel on the front and sides. At 2 millim. behind each of these teeth 
is the socket of a smaller premaxillary tooth; this tooth apparently 
had a thin wall and a pulp-cavity relatively larger than in the 
anterior tooth. It is separated by a ridged diastema from the 
series of six molar teeth on each side, the first of which has a sub- 
triangular crown with the base applied to the second tooth. The 
latter and the four following teeth are nearly similar, subquadrate 
in form, with the crowns “impressed by a pair of antero-posterior 
grooves, dividing the grinding-surface into three similarly disposed 
ridges, and each ridge is subdivided by cross notches into tubercles. 
Of these there are, in the second to the fourth molar inclusive, four 
tubercles on the mid ridge, three on the inner ridge, and two on the 
outer ridge.” 
The author discussed the relations of this new form of mammal, 
