112 AMERICAN MARINE CONCHOLOGY. 
tenanted by their singular molluscan 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, Muller. 229. 
(Doris.) Zool. Dan. Prodr., 229. 1780. 
Tritonia Reynoldsit, Couthouy, 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 pulchella, Alder and Hancock, Ann. Nat. Hist., ix. 33. 
Body tapering to the tail, which ends acutely; sides with nu- 
merous papilla; 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. ropustus, Verrill. Fig. 230. 
Am. Journ. Sci., 1. 405, f. 1. 1870. 
Eastport, Maine; Grand Manan Island. (Hur.) 
Family DOTONID A. 
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 
branchiz 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. 
