The two younger specimens have the clear border and accessory plate less developed, and very young ones do not probably show these characters at all, but resemble the typical _Aplysia_ in the form of the shell. On this account I am unwilling to constitute it a new genus, but propose to call it a sub-genus under the name of NEAPLYSIA. There was no appearance of a multiplication of shells, said to occur in old specimens of _Aplysia_. Not having any full description of the internal anatomy of _Aplysia_, I cannot at present determine whether there are many other differences in structure. The stomach was full of large fragments of _Algæ_. I found three specimens only, on the beach at San Pedro, July 25th, just after a heavy blow which occurred at the lowest summer tides. Kept in water for some time, they were very slow and uninteresting in movements, showing no evidence of any means of defence except the exudation of a beautiful purple fluid from the mantle when handled. This fluid, common to the Aplysiæ, though formerly supposed to be poisonous and indelible, possesses no such properties, though it may be a defence against marine animals which attack them. The figure, taken from a tracing of the shell, and electrotyped by Dr. A. Kellogg, represent the inner surface of the most developed specimen, of the natural size. [Illustration: FIG. 14.] NAVARCHUS, Cooper, Proc. Cal. Acad. Ap. 1863. _N. inermis_ Cooper. Syn. _Strategus inermis_ Cooper, Proc. Cal. Acad. II, 1862, p. 202. One small specimen, dredged among seaweeds in ten fathoms, near the eastern shore of the “Isthmus,” Catalina Island, shows no variation from those obtained at San Diego. DORIS, Linn. _D. albopunctata_ Cooper. State Coll. Species 1000. Form ovate, pointed behind, flattened, surface shining, minutely rugose. Tentacles club-shaped, retractile, branchial plume, 6-8 parted, bipinnately divided, situated near the posterior extremity. Color yellow or orange brown, dorsal surface thickly speckled with small white dots, each forming a slightly raised papilla. Beneath paler. Dredged from a rocky bottom in twenty fathoms, a mile from the shore at Santa Barbara. Also found on rocks at low water mark near the north-west end of Catalina Island. Length about one inch, breadth one-third of an inch. _Doris montereyensis_ Cooper, Proc. Cal. Acad. II, 1862, p. 204. Found at Santa Barbara Island on rocks at low water, differing from the original specimens only in larger size and deeper color. The tentacles are club-shaped, the branchial 7-8 parted, bipinnate and from one opening. _Doris sanguinea_ Cooper, loc. cit. (_Asteronotus._)