DOTO. 237 



obliquely truncated. Branchiae ovate clavatc, attached by a slender 

 base, arranged in a single line of five to eight on each side, the pos- 

 terior pairs quite small and short, encircled with tubercles which 

 are capalde of considerable contraction and elongation, each one 

 tipjjed with a dark-red spot, sometimes nearly black ; its pith is of 

 a similar dark color. Foot pale yellowish, transparent, somewhat 

 bi-lobed in front. Length, about half an inch. 



Found at Craigie's Bridge Bath-house ; on the piles of the bridge 

 below low-water mark (^Slimpson) ; dredged in Vineyard Sound 

 (^A^assiz^; dredged in fifteen fathoms, near Duck Island (Stimp- 

 son) ; Xahant {Alex. Ag-assiz} ; Gloucester (1865) {Mrs. Smith). 



A l)eautiful animal, and readily recognized by its club-shaped 

 branchias, covered with more or less dark-red dots ar- 

 ranged in circles. It is very variable in color, varying 

 from almost colorless to deep brown, so that several 

 names have been attached to mere varieties. Profes- 

 sor Agassiz had proposed the name arbuscula* for a 

 specimen found by him ; and I myself had chosen the 

 name lycopodina, from the resemblance of the branchicB 

 to the clubs of Lycopodinus. It differs from D. pin- ova of r>. cow- 

 natifida in not having a range of tubercles along the " /' 



outer margin of the animal, and in having the bran- 

 chial tubercles less elongated. In D. fragilis the clubs are cone- 

 like, the imbricating tubercles not dark pointed. 



Spawn clings to small zoophytes in large, flattened, convoluted 

 strings, in the early part of June. 



Family J^OLIDID^. 



Tongue narrow, teeth in a single central series ; jaws liorny. 

 Tentacles suljulate, simple, rarely ringed, contractile. Gills super- 

 ficial, fusiform or branched, on the sides of the back. Vent lateral. 



In the family of jEolids the curious tentacular sheaths, which are 

 present in many of the other tribes of Nudibranchs, appear to be 

 altogether wanting ; the orifices of the generative system and vent 

 are situated at the right side, and the gills, usually papillose, are 

 arranged in rows along the sides of the back. 



* A drawing of Professor Agassiz's original specimen left no doubt in Dr. Gould's 

 mind of the identity of the two. — W. G. B. 



