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 posteriori)' in a 

 hollow cup or cone, which has several diaphragms within it, and is 

 not covered outside and behind by a solid chitiiious spine as is the 

 case with most, perhaps all, Onyclioteuthids ; 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 lladula has only five rows of teetli, 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 tlie usual form, having a valve, as has already been re- 

 corded by several observers, although Grray denied its existence. 



The two retractor muscles of the siphon (depressores infundibuli, 

 m, m) are seen stretching backwards from its base on either side, 

 and external to them are the gills {br.), 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 (i.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 {br.h.) in their usual situation. 

 The renal openings seem to be minute papillae, 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 oviduct (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 («) 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 Cephalic Cartilage. — Two heads of larger specimens were 



9* 



