TRITONIA HOMBERGII. 



This fine nudibranch — the giant of its tribe —is stated by Diquemare, to reach the length 

 of eight inches ; and Sir J. G. Dalyell has found it of similar size, but it is seldom met with 

 of a greater length than six inches, and usually it does not exceed four. It is a deep-water 

 species, very generally diffused, but seldom obtained except by the dredge or trawl; 

 occasionally, however, it is brought in on the fishermen's lines. In its young state it is less 

 plumose and warty than the adult form. The spawn is deposited in the form of a gelatinous 

 yellowish- white cord, about the thickness of small whip-cord of great length and very much 

 convoluted. The eggs are disposed in it about five or six abreast, without regular order. 

 Sir John G. Dalyell gives a detailed account of the spawning of this animal, in the second 

 volume of ' The Powers of the Creator displayed in the Creation,' page 275. In reading it, 

 however, it will be necessary to bear in mind that the author confounds two species, and that 

 the smaller masses of spawn figured probably belong to Tritonia plebeia. 



Professor Edward Forbes mentions two varieties on the coast of the Isle of Man, — a 

 purple and a yellowish variety, — the latter is generally longer than the former (often six inches 

 long) and has the branchiae smaller. The Tritonia atrofusca of Macgillivray was described 

 from a very dark variety of this species, examined in a dead state. The specimen is in our 

 possession, having been obligingly presented to us, along with his other Aberdeenshire 

 Nudibranchiata, by Dr. Macgillivray. His genus Spharostoma is also founded upon a specimen 

 of T. Hombergii, in a bad state, as has been before mentioned. 



Tritonia Hombergii is very sluggish in its movements, and is not easily kept in confine- 

 ment. It discharges a great quantity of mucus. As might be inferred from its immense 

 jaws, it is a very voracious animal. M. Bouchard Chantereaux states that its principal food 

 is the Alcyonium digitatum, which is confirmed by the observations of Sir J. G. Dalyell. The 

 former naturalist has also frequently found individuals between the valves of oysters, of 

 which they had partially devoured the animal. We have taken from the digestive cavity of 

 this animal large lumps of the tube of Amphitrite ventilabrum, with the Alcyonium adhering 

 to it. 



The range of Tritonia Hombergii is nearly co-extensive with the Atlantic shores of 

 Europe, but it does not appear to reach into the Mediterranean. 



Figs. 1, 2, Side and back views of Tritonia Hombergii. 



3, Under side of the anterior portion of the same. 



4, A portion of the cloak enlarged. 



5, A few of the tubercles in profile. 



6, A portion of a branchial plume. 



7, A tentacle. 



