112 AMERICAN MARINE CONCIIOLOGY. 



tenanted by their singular mollnscan inhabitants, thus serve in 

 some measure to enliven the solitude of the ocean. 



Genus DENDRONOTUS, Alder and Hancock. 



Tentacles clavate, laminated ; front of head with branched ap- 

 pendages ; gills ramose, arranged in a single series down each side 

 of the back. 



1. D. ARBORESCENS, Midler. 229. 



{Doris.) Zool. Dau. Prodr., 229. 1780. 

 Tritonia Eeynoldsii, Coulhouy, Bost. Journ. Nat. Hist., ii. 74, t. 2, f. 1-4. 



1838. 

 Tritonia lactea, Thompson, Ann. Nat. Hist., v. 88, t. 2, f. 3. 

 Tritonia pulcJiella, Alder and Hancock, Ann. Nat. Hist., ix. 33. 



Body tapering to the tail, which ends acutely; sides with nu- 

 merous papillae ; head short, depressed, orbicular, supporting three 

 pair of gills ; mouth crescent-shaped, papillose, with strong trans- 

 verse folds ; jaws angular ; tentacula arising from the back of 

 the head, and received into a round sheath, which terminates in 

 five unequal branches ; five pair of dorsal gills, all susceptible of 

 being retracted into the body of the animal, leaving in their places 

 small tubercles; rufous brown, occasionally dark brown, with 

 patches of white on the back between the branchial tufts ; foot 

 white, diaphanous. 



Length 3.5 inches. 



New England ; Northern Europe. 



2. D. ROBUSTUS, Terrill. Fig. 230. 



Am. Jouru. Sci., 1. 405, f. 1. 1870. 



Eastport, Maine; Grand Manan Islaiid. (Eur.) 



Family DOTONID^. 



Genus DOTO, Oken. 

 Lehrb. Naturg. 1815. 



Head covered by a simple veil ; tentacles linear, sheaths trum- 

 pet-shaped ; gills clavate, compound, or rough, with whorls of 

 tubercles ranged in a single series on each side of the back. 



The tentacular sheaths have simple margins, and the ovate 

 branchiae are rough with tubercles ; the front of the head is sim- 

 ple, and the foot is linear ; they appear to feed on hydroid zoo- 

 phytes. 



