Brain of Mastodon giganteus. — 49 
and were probably the third and the fourth of the dental series 
—the empty socket in front corresponding in size with the wesond 
two-ridged tooth 
mong the anatomical points of interest which have not as 
yet been especially described, are the number and proportional 
size of the foramina in the base of the sknil; and the form of 
the brain as indicated by the configuration of the cranial cavity. 
Olfactory Joramina.—The eribriform: plate on either side of 
the median lines is of a pyriform shape; it is about two and’ 
six-eighths inches in length by one and six-eighths in breadth, 
and is perforated by a large number of minute holes for the trans 
mission of the filaments of the olfactory nerves. Of these open- 
ings one hundred and seventy-five were counted on one side. 
An a larger than the rest exists at the upper part and serves 
xit of the nasal branch of the fifth pair of nerves. 
The Optic foramen is vertically depressed having an elongated 
oval form ; but as the optic canal recedes from the cranial cavity 
it becomes more hearly cylindrical, having a diameter of about 
three-sixteenths of an inch; the canal is directed upwards for the 
distance of os inches when it reaches ~ orbit in the bottom 
of a deep ch annel. 
The Foramen lacerum of the orbit is —_- small, Nes ‘eon: 
cealed beneath the anterior clinoid process, and is so mach out 
of view that it would easily escape notice’: it enters the orbit 
. same harmel with tne —_ nerve, but some erage be-" 
OW it. 
{o the cranium of in -adnlt: Affican elephant belonging to ‘he 
ty of Natural History, and which has served for the 
comparisons given in this notice, the ple -lacerum is more 
€xposed within the cranium, and its ou re oN § is separated 
only by ree ‘septum of bone from that of the optic pomp 
canal is last being much shorter than in the Masto 
Sarinees rotundum which transmits the second aoe of 
ona Tigemninus nerve, is about one half of an inch in diameter, 
very nearly the position of the foramen lacernm of 
the heres in other avimals it is only separated from this last by a 
thi bridge of bone; and this even no longer exists in some Ru- 
whlly bi so that in these the foramen lacerum and rotundum are 
rman ovale measures an inch and a quarter in length 
and half an inch in breadth, but is partially divided, by slight 
Projections of bone on each “sides into a double opening. It is 
formed main ‘mainly by the edge of the great wing of the sphenoid, 
cumference posteriorly i is completed by the petrous bone. 
‘inner part of this foramen transmits the third branch of the 
rigeminas, while the outer portion is continuous with a channel 
‘D Series, Vol. XV, No, 43.—Jan., 1853. 7 
