The following species were collected while exploring for the State Geological Survey, along the main land and islands bordering Santa Barbara channel, in May, June, and July last. Besides those described as new, I obtained additional specimens of some of those described in 1862, confirming the specific characters then given, and to some extent establishing the generic more accurately. Careful notes and drawings from living specimens furnish the basis of most of the descriptions, together with examination of the specimens in alcohol. With regard to localities, it must be noticed that “Santa Barbara” and “Santa Barbara Island” are very distinct both in local characteristics and the groups of animals inhabiting them. The island is about seventy-five miles from the town, and thirty-five from the nearest main land. Catalina Island is twenty-four miles from the main land, and very different in its molluscous animals from both the main land and the other islands, being the richest locality on our shores. I have not been able to compare these species with those from South America described by D’Orbigny and others; but, like our other littoral mollusca, they are probably distinct. I have, however, found the pelagic species _Ommastrephes giganteus_ D’Orb in large numbers, and “hundreds” of a species of _Argonauta_ washed ashore last spring as far north as Santa Cruz Island, as I was informed by Dr. Shaw, who presented specimens to the State collection. APLYSIA Linn. _A. californica_ Cooper. State Collection, species 1045. Form and external appearance as usual in the genus. Length fifteen inches, breadth five, height about the same. Color pale gray or greenish, becoming purplish on the side, folds of mantle with scattered white specks, from which an irregular network of brown lines extends over the rest of the body, interspersed with large brown blotches. Inner surface of mantle varied with alternating painted bars of white and dark brown interlocking together. Sole of foot black. Eyes very minute and black. _Shell_ contained in the substance of the mantle cartilaginous, translucent, trapezoidal or hatchet-shaped, margins rounded, slightly convex above, the nucleus or centre in old specimens distant from the posterior end or apex. Faint radiating lines diverging from the nucleus, crossed by an irregular network of darker lines, all ending abruptly at some distance from the margin, which has thus a wide, nearly transparent border. An accessory plate arises on the inner surface from the nucleus, spatulate in form and slightly raised.