MOLLUSCA. TRITONIA. 5 



branchiae fringed, arranged in a semicircle. All the tubercles, 

 the tentacula, and the branchiae are tipped with a bright sulphur- 

 yellow color. Length | and breadth I of an inch. Found in 

 the Bathing-house at Craigie's Bridge, Boston. 



Another family of the Nudibranchiata have the branchiae dis- 

 posed in numerous tufts along the sides and back (Polybranchidta, 

 Blainv.), and they are not capable of being entirely retracted. 

 The anal orifice also is found on the right side. 



Those which have the branchia; arborescent, and the tentacula 

 about the mouth somewhat fringed, constitute the genus Tritonia. 

 We have one species of this genus. 



Tritonia arborcscens, Cuv. ; Mem. du Mus., vi. 28, pi. 1, 

 f. S-10. Doris arborescens, MIill. and Fabr. Tritonia Rey- 

 nuldsii, Couthguy ; Bost. Journ. Js\U. Hist., ii. 74, pi. 2, 

 f. 1-4. 



Mr. Couthouy found them about the bathing-houses and timber- 

 docks in Charles River, of singular size and beauty ; and his de- 

 scription and the figures illustrating it,, are such as to give us an 

 idea of the animal to the life. He found that the specimens 

 he observed differed in some respects from the details given by 

 Cuvier of T. arborcscens ; and therefore he instituted a new spe- 

 cific name. But, making allowances for the distortion of Cuvier's 

 specimens, which had doubtless been immersed in spirits, and 

 adding the assurance of Dr. Lovtn, that the living T. arborcscens 

 corresponds exactly with Couthouy's description and figures, we 

 have reason to conclude, that the animal observed by the two 

 naturalists is the same. 



Nothing can be more singular than this slug-like animal, mottled 

 with brown and white, overspread with numerous wart-like ex- 

 crescences, and apparently bearing some fifteen or twenty widely 

 and numerously branched plants, which are the branchiae. There 

 are six pairs of these, including the tentacula, besides the three 

 pairs about the mouth. 



Genus Eolis, has two or three pairs of simple tentacula, one 

 of which is in the vicinity of the mouth ; and the branchiae, in the 



