The first was a White Dendronotus (Dendronotus albus). The standout feature of this species are the cerata (dorsal projections) on the back — "delicately branched" and tipped with white and orange.
The second species was a Chocolate Cuthona (Cuthona cocoachroma). Note that the centers of the cerata are chocolate brown. The frosted white tips of the cerata are also distinctive.
Both of these nudibranchs were feeding on hydroids in tidepools in the low intertidal zone.