ON THE MANATEE. 309 
_ The rudiment of the urachus is more preserved than usual; and 
from the anterior extremity of the bladder a fine tube extends along 
its axis for a short distance. 
Dr. Murie has described and figured the brain. He, however, 
mentioned that the specimen he examined was not in the most fit state 
for investigation. I was able to remove the organ within twenty- 
four hours of the animal’s death, when it was not in the least injured ; 
my opportunities have therefore been more favouravle, and the 
differences I have detected make me think it-better to give fresh 
illustrations of its conformation. The brain does not present con- 
volutions properly so called. The Sylvian fissure is large and bifur- 
cates high up; it ceases some way externally to the main longitudinal 
fissure of the brain; it also separates sufficiently at its origin to show 
the situation of the Jobus opertus. A hippocampal sulcus also gives 
origin to the hippocampus major. There are distinct indications of a 
superior frontal sulcus. The calloso-marginal sulcus is well marked, 
continuous, and extends far back, ceasing in front opposite the genu 
of the corpus callosum. Below this point the frontal lobe extends a 
great distance, as is clearly shown by Dr. Murie, and it presents 
slight indications of sulci on its antero-inferior angle (vide Plate [13] 
The corpus callosum is short from before backwards, and in a 
median longitudinal section only covers the anterior and a little of the 
superior border of the thalamus opticus. Between it and the fornix 
no septum lucidum is developed, the precommissural fibres forming a 
thick median longitudinal plane, extending from the corpus callosum 
to the fornix. The anterior white commissure is small, as in the pineal 
gland. The corpora quadrigemina are not large. 
There is no trace of a posterior horn to the lateral ventricle. The 
hippocampal sulcus, however, extends so far up above the posterior 
portion of the thalamus opticus as to develop the basal part of the 
hippocampus major into a triangular lobule, partly obliterating the 
back of the lumen of the cavity of the lateral ventricles, and bounded 
along its base-line, which runs from behind and externally forwards 
and inwards, by the ample fringe of the choroid plexus. The anterior 
horn of each lateral ventricle is deep, in correlation with the great Page 143. 
extent of the lobe it excavates. The walls of the cerebral hemi- 
spheres are not at all thick, the lateral ventricles being capacious. 
Professor E. R. Lankester being specially interested in the ques- 
tion as to the cervical nerves, dissected them out in the specimen 
under consideration. The following are his notes on the subject :— 
““ Dr. Murie, in his paper on the Manatee, states that in a specimen 
dissected by him there were eight pairs of cervical nerves, of which 
two pairs issued between the second and third cervical vertebre. 
