NAKED-GILLED SUBGROUP 



3327 



ularly white-edged dorsal eye spots. It is vividly phosphorescent in the dark, and 

 the phosphorescence at once appears if 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 eight 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 seven or eight inches in length. It varies 

 in color from dark purple brown to light brown, flesh color, and yellowish white. 

 Dendronotus arborescens is one of the most beautiful of the naked Molluska, the 

 figure on p. 3326 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, that the 



Phyllirhoe bucephala IN THE LIGHT, SHOWING INTERNAL ANATOMY (greatly magnified). 



head veil is also branched, and 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 two 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 Greenland. 

 It is also recorded from the Atlantic coasts of North America, north coast of France, 

 and some parts of the Baltic. The animals belonging to the genus Scyllcza live upon 

 floating seaweed out on the high seas; 6*. pelagica being usually found upon the gulf 

 weed of the Atlantic, which it resembles in its coloration. The foot is narrow, the 

 sides being thin, and capable of clasping the stems of the seaweed. The body is 

 much compressed laterally, and produced into two large leaf -like appendages on 

 each side of the back, on the inner surface of which the tufted branchial processes 

 are situated; a median supra-caudal crest also bearing branchial filaments. The 



