374 PROCEEDINGS OF THE CANADIAN INSTITUTE. 
rest of the retina, but unlike Anguilla there are no retinal vessels. 
So far as I have observed the lens, its capsule, campanula Hallert and 
processus falciformis offer no exceptional features. 
AUDITORY ORGAN. 
In many respects the labyrinth of Amiwrus resembles that of the 
Cyprinoids. The pars super/or and inferior are equally widely sepa- 
rated, and while the connecting narrow but thick-walled ductus sac- 
culo-utricularis is very distinct, the pars inferior lies largely behind 
the pars superior. The latter is especially distinguished by the large 
size of the recessws utriculi, and of the contained macula and otolith 
(lapillus), Fig. 9, Pl. I. Unlike the pars inferior it lies comparatively 
free in the cranial cavity, except for certain parts of the semi-circular 
canals. The wall of the skull opposite the fovea rec. utr. is extremely 
thin, but over against the thin-walled wtriculus is much thicker. 
Where the ductus sacculo-utricularis opens into the pars inferior, the 
latter also looks freely into the cranial cavity. At this point the 
fovee sacculi, which are hollowed out on the upper surface of the 
basi-occipital bone, are separated from each other by a median crest, 
somewhat wider anteriorly, where the anterior tips of the sacculi 
(processes of Comparetti)! diverge forwards into small recesses of the 
prootics. To this crest the wall of the labyrinth is attached, as repre- 
sented in Figs. 8 and 9, P]. VI.; the relationship to it of the posterior 
branches of the auditory nerve is seen from the same figures. Fur- 
ther back the fovee are separated by the median cavum sinus im- 
paris ; whose floor is hollowed out in the basi-occipital, but whose 
walls and roof are furnished by the ex-occipitals. The relationship 
of these cavities may be gathered from Fig. 15, Pl. IV., which repre- - 
sents a frontal section through the head of a young fish of 3-4 ctm., 
and from the figures on Plate VI. It will be seen that the ex-occipi- 
tals also form the lateral wall and roof of each fovea sacculi, and that 
especially the lagene cochlee are lodged in these bones. 
Figs. 9 and 10, Pl. 1, represent the medial and lateral aspects of the 
labyrinth. The relative position of the /agena cochlew, and saceulus, 
and of the contained macule acustice, may be better seen from Fig. 15, 
Pl. IV. The otoliths which rest on the macule acustice of the 
recessus utriculi, lagena cochlee, and sacculus respectively, and which 
1 Hasse :—Auatomische Studien I., 592. 
