GASTROPODS. 
357 
and the blackish irregularly white-edged dorsal eye-spots. It is vividly phosphor¬ 
escent in the dark, and the phosphorescence at once appears it* the creature is in 
any way disturbed. It is said to be 
lively in its movements, and capable of 
swimming freely in any direction; but 
has neither jaws nor radula. Specimens 
are sometimes captured 8 inches to a 
foot in length. In the genus Tritonia 
the branchiae are numerous, and arranged 
in a row along the lateral margins of 
the back. There is a large frontal veil 
above the mouth as in Tethys, and the 
retractile tentacles are branched at the 
ends. The horny jaws are large, and 
the radula well developed. T. hombergi 
is the largest of the British nudibranchs, 
being sometimes 7 or 8 inches in length. 
It varies in colour from dark purple- 
brown to light brown, flesh-colour, and 
yellowish white. Dendronotus arbor- 
escens is one of the most beautiful of 
the naked Mollusca, the accompanying 
figure giving a good idea of the 
branched character of the gills. It 
will be noticed that they are arranged 
along each side of the tapering body, Tethys leporina. 
that the head-veil is also branched, and 
Dendronotus arborescens (enlarged) 
that the laminated 
tentacles are retractile 
within branched 
sheaths. The back 
is reddish or yellowish 
brown, marbled with 
darker brown, and 
spotted with white. 
The animal is about 2 
inches in length, and 
has both jaws and 
radula. It is not 
uncommon on most 
parts of the British 
coasts, from low-water 
mark to deep water, 
and it also ranges 
northward to Green¬ 
land. It is also re- 
