ENDOCRANIAL ANATOMY OF FOSSIL MAMMALS ao 
separating the lobus anterior from the lobulus simplex. The 
lobus anterior is wholly without lamellae or other complexities. 
The lobulus simplex is merely a narrow band running across the 
posterior surface of the endocranial cast. The lobulus petrosus, 
the lower part of the pars floccularis, is represented in both speci- 
mens. It stands out so sharply as scarcely to be recognizable 
as a part of the cerebellum. It is a smooth rounded object 
some 3 mm. in diameter attached by a narrow pedestal to the 
side of the cerebellum. 
Carnivora (Aeluroidea) 
Dinictis felina Leidy. The most primitive cat represented in 
the present assemblage of endocranial casts is Dinictis felina 
Leidy from the Oligocene of South Dakota. The cast (figs. 3 
and 4) is an unusually good one, as such objects go, though the 
olfactory portion is imperfect and the cerebellar portion obscured. 
The form of the cerebrum is, however, almost perfect and one 
may see at a glance its typically feline character. 
When Scott (’89) discussed the systematic position of Dinictis 
he referred to it as the most primitive cat then known. Later 
(13) he maintained this position and referred to the opinion of 
others that Dinictis was in a direct ancestral line with the modern 
cats. The genus is usually referred to the machairodonts or 
saber-toothed cats, a line of forms which culminated in the 
huge Pleistocene species (fig. 16), but was also doubtless close to 
the stem form from which the modern cats were derived. 
The cranium of this light-limbed, cursorial machairodont is 
somewhat elongated, the upper contour of which slopes sharply 
downwards and backwards from the highest point of the cranium, 
just back of the orbits, thus leaving but little room for the brain- 
case. The face in advance of the orbits is much contracted. On 
account of these cranial formations, the space allotted the cere- 
brum is comparatively short, while the cavities of the hind-brain 
and olfactory lobes are long (Scott, ’89). At the time Scott 
wrote, nothing was known of the form of the brain, save in a 
general way, and, so far as I am aware, no one has since studied 
the cerebral form of Dinictis. 
