1889.] ANATOMY OF GONATUS FABRICII. 119 
5. The Gladius is narrow and linear anteriorly, but broader and 
lanceolate in the hinder two thirds, whilst it ends posteriorly in a 
hollow cup or cone, which has several diaphragms within it, and is 
not covered outside and behind by a solid chitinous spine as is the 
case with most, perhaps all, Onychoteuthids; at all events no 
species hitherto known has such a hollow cone. 
6. The Fins extend some distance beyond the hinder end of the 
body, and their firm saddle-shaped cartilage slides upon the terminal 
portion of the gladius. 
7. The Radula has only five rows of teeth, instead of the usual 
seven. 
II. General Disposition of the Organs. 
The mantle-cavity is very extensive, reaching backwards almost to 
the end of the caudal extremity ; when it is opened the following 
arrangement of parts may be observed (Plate XIII. fig. 5). The 
siphon is of the usual form, having a valve, as has already been re- 
corded by several observers, although Gray denied its existence. 
The two retractor muscles of the siphon (depressores infundibult, 
m, m) are seen stretching backwards from its base on either side, 
and external to them are the gills (47.), which are very long and 
fixed to the mantle almost as far as their ends. Attached to the 
base of the siphon, to the lateral aspect of the head, and to the mantle 
in the middle line above is the usual valvular flap formed by the col- 
laris muscle, which prevents the egress of the water from the lateral 
parts of the mantle-cavity. 
The ink-sac (7.s.) lies in the middle line and extends forwards 
almost to the anus (a.): in the larger specimen it was quite fragmen- 
tary, but appeared to reach further backwards than in the small 
ones, in which, moreover, it was somewhat obliquely placed. The 
rectum passes over it forwards from right to left, and the anal flaps 
(in the small examples) are simple in form, and taper gradually from 
the base to the apex. The vena cava (v.c.) lies along the right side 
of the digestive gland (“ liver” of most authors). 
Through the renal sac may be seen the sacculations on the vena 
cava (re.) and the branchial hearts (67.A4.) in their usual situation. 
The renal openings seem to be minute papillze, situated just in front 
of the branchial hearts, as in Onychoteuthis. One of my specimens 
showed them, and I was able with some difficulty to make out 
their position in a specimen in the British Museum. The apertures 
of the cviduct (Plate XIII. fig. 3, od.) are deeper than and external 
to the branchial hearts, and the nidamental glands may be seen in the 
middle line immediately posterior to the renal organs: .the posterior 
aorta passes out between their diverging hind extremities. 
In the smaller specimens the stomach (s) could be discerned in 
the middle line behind the bases of the gills ; the genital gland when 
fully developed appears to cover it. 
III. The Cartilages. 
The Cephaiic Cartilage——Two heads of larger specimens were 
g# 
