No.3.] MUSCLES AND NERVES IN AMIA CALVA. 509 
The lobus lies partly in front of, and partly under, the median 
two thirds of the corresponding hemisphere of the fore-brain, 
the upper and lateral surfaces of which, in their posterior por- 
tion, show well-marked convolutions, much stronger than Gage’s 
figures and reference to them (No. 40, p. 296) would seem to 
indicate. Ventrally the lobus extends further backward than 
on its dorsal surface, and there is no line of demarcation between 
it and the base of the fore-brain beyond it, as Gage has already 
stated (No. 40, p. 297). On the sides and dorsal surface, on the 
contrary, it is sharply limited and defined by a deep fissure or 
furrow, which, on the median side of the lobus, lies just in front 
of the lamina terminalis, and separates that structure, exter- 
nally, from the lobus. The fissure, therefore, at this point is 
the fissura prima. In the remaining portion of its course it 
seems to be the sulcus olfactorius of Burckhardt in Protopterus, 
but it is evident to the most superficial observation that the fis- 
sure and sulcus of Amia have not the position that they have 
in Protopterus, and that the lobus of Amia contains elements 
not found in the tuberculum of Protopterus. Lee’s conclusion 
(No. 72, p. 5) that the latter structure is in reality a lobus, 
strictly comparable to the lobus of other animals, may therefore 
be questioned. It seems more probable that it is a bulbus 
partly separated from the fore-brain. 
In embryos of Amia the sulcus olfactorius extends across the 
ventral surface of the brain, and a continuous groove is thus 
formed, running backward and outward across the dorsal surface 
and backward and downward across the lateral surface of the 
brain, then across its ventral surface, and then forward and 
upward along its median surface between the lobus and the 
lamina terminalis. 
The olfactory diverticulum is, in 12 mm. and 14 mm. speci- 
mens, short and broad, extends outward and forward from the 
median or median and upper portion of the basal ganglion of 
Goronowitsch, and has at its anterior and lower portion a 
pointed prolongation, apparently the true recessus olfactorius, 
extending forward into the lobus. In its hinder portion, exactly 
where Studnitka (No. 122) describes and figures the cornu pos- 
terior of the ventriculus lateralis in Petromyzon, it has a sharply 
