On the Skull of Tritylodon longeevus, Owen. 283 
XXXI.—On the Skull of Tritylodon longeevus, Owen. 
By Dr. BRANISLAV PETRONIEVICS. 
[Plate X.] 
SINCE Owen described in 1884, for the first time as mammalian, 
the skull of the single specimen of T'ritylodon existing in the 
British Museum, several authors have re-examined his state- 
ments. Seeley, in 1888, declared Tritylodon to be a 
“bunotheroid Rodent”; but in 1894, after his discovery 
of Gomphodontia, he gave up this opinion and declared 
Tritylodon a ‘ theriodont Reptile”’ or as “ intermediate 
between Mammals and Theriodonts.” R. Broom, in 1904, 
showed that the reasons of Seeley for the statement that 
Tritylodon was a reptile are not tenable. In 1910, after 
having studied the specimen, Broom established the presence 
of new sutures between bones which had been wholly over- 
looked by the earlier observers, and so reinforced his opinion 
that Tritylodon is a true mammalian. 
Having examined the specimen at the end of last year 
while in London, I believe that some new sutures can be 
made out, and that the limits between the bones are somewhat 
different from those established by Broom. A new prepara- 
tion of the specimen has also cleared up some controversial 
points. 
Text-fig. 1 shows the upper view of the skull. The 
plainest suture is that separating on the left side for some 
distance the nasal from the maxillary. In the front part of 
this suture begins another, which is for the first time plainly 
to be seen only with a magnifying-glass (it lies just above a 
zig-zag crack). The prolongation of this latter suture on the 
right is not clearly indicated, but is probable. IPfso, the whole 
would separate the nasal from the frontal; but it is not 
impossible that the visible part separates the lacrimal from 
the nasal. 
The sutures separating the prefrontal from the frontal and 
lacrimal are doubtful or not at all indicated. The right side 
is so damaged that only the suture bounding the maxillary is 
to be seen for some distance. 
The septomaxillaries, first observed by Broom, are now, 
after the new preparation, plainly (comp. text-fig. 1 and the 
photograph of the nares in Pl. X. fig. 1) to be seen, They 
limit the nares laterally, cross them from below, and send a 
short joint process above, which seems to meet in the middle 
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