In the “Mollusca and Shells,” of the U. S. Exploring Expedition under Commodore Wilkes, Dr. Gould mentions a species of Dendronotus collected at Puget Sound, but does not name it or give any clue to its characters, except that the _branchiæ_ have white tips, unlike our specimens. It is very probable, however, that it belongs to the same species, as so many of the Mollusca of this coast have an equally wide range. ÆOLIS Cuvier, 1798. _Æ. barbarensis_ Cooper. State coll. species 978. Rose-red, longer tentacles tipped with yellow, branchial ciliæ simple, in six longitudinal rows, all short, the middle rows longest and tipped with blue, anterior tentacles two, above the mouth, dorsal tentacles club-shaped, a white streak extending from the median line between them to the mouth. Length nearly an inch. One specimen dredged on a rocky bottom, in a depth of 16 fathoms, a mile from the shore at Santa Barbara. Although small, its characters are too different from those of our other species, when of the same size, to allow us to consider it the young of any of them. FLABELLINA Cuvier, 1830. _F. opalescens_ Cooper. _Syn._ Æolis, (Flabellina?) opalescens, Cooper—Proc. Cal. Acad. II, 1862, p. 205. This species, dredged from the same locality as the last, presented exactly the same characters as the original specimens from San Diego. I also found a few of them on the rocky shore of Santa Barbara Island, differing only in having the branchial olive, tipped with white. PHIDANIA Gray, 1850. _P. iodinea_, Cooper—_Syn._ Æolis (Phidania?), iodinea, Cooper, loc. cit. sup. I found one of this species on the beach at Santa Barbara, agreeing exactly with those from San Diego. CHIORÆRA Gould, 1855. _C. leonina_ (?) Gould—Molluscs and Shells, U. S. Expl. Exped. Wholly translucent, pale yellow, the variations marked only by a darker shade. Form of head nearly conical, the apex anterior, forming an angular roof above the oral opening. Bronchial processes five on each side, larger than represented in Gould’s figure, imbricated and decumbent. Length 2.75, height 1 inch. Otherwise as in the description and figure of Gould’s specimen. A single specimen dredged in 20 fathoms off Santa Barbara, May 15th, differs in the points above mentioned from the northern animal, but being much smaller, the differences may arise from immaturity, and I have therefore preferred to retain the same name for it.