We document development type for 33 species of benthic opisthobranch gastropods – 15 for the first time – collected mainly from the Southern California Bight. Fourteen of the newly examined species had planktotrophic development, while the dorid nudibranch Atagema alba had capsular metamorphic development, the first example of direct development in a non-dendrodoridid nudibranch known from the northeast Pacific Ocean. For the remaining 18 species our new data are either consistent with earlier determinations of development type, or confirm previous inferences. The new data also broaden geographic coverage for some species, and for the sacoglossan Stiliger fuscovittatus and the nudibranch Melibe leonina, suggest that egg size is inversely related to temperature. We correct the previous erroneous identification of nephrocysts as eyespots in the hatching planktotrophic larvae of the nudibranchs Tritonia festiva and Janolus fuscus. These results further highlight the predominance of planktotrophic development in benthic opisthobranchs from the northeast Pacific Ocean.