Key:  Order Nudibranchia Suborder Cladobranchia Superfamily Arminacea

Phylum Mollusca
 Class Gastropoda
  Subclass Opisthobranchia
   Order Nudibranchia

Taken primarily from  Kozloff, 1987, 1996  p. 254 (Copyright 1987, 1996, University of Washington Press.  Used in this web page by permission of University of Washington Press)
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1a  Without cerata: dorsum with several white longitudinal ridges on a pinkish brown background (these ridges converge anteriorly toward the rhinophores) (on sandy substrata) Armina californica
1b With cerata; dorsum without white longitudinal ridges 2
2a Cerata slender, circular or only slightly oval in cross-section, and approximately the same diameter over most of their length; without a prominent oral veil. 3
2b Cerata leaflike (broad in the middle and tapering toward both ends), distinctly flattened in cross section; with a prominent oral veil on the head 4
3a Body whitish, translucent, without blue spots on the dorsum; with an irregular dorsomedial red band (this may be interrupted) running from in front of the rhinophores to near the last pair of cerata; crest between the rhinophores distinctly red; terminal portions of cerata with a proximal orange band followed by a transparent colorless band and finally by an opaque white tip. (Janolus fuscus in original key) Antiopella fuscus
3b Body whitish, translucent, with small (visible with magnification) blue spots scattered over the dorsum; without a dorsomedial red line; crest betewen the rhinophores sometimes pale orange but not red; terminal portions of cerata with a proximal orange band succeeded by white, or with an orange band succeeded by white bands and finally by blue bands. (Janolus barbarensis in original key) Antiopella barbarensis
4a Body orange, with white splotches on the dorsum (with white lines on the eges of the cerata, but not around the foot and oral veil, or between the rhinophores) (Dirona aurantia in original key) Dirona pellucida
4b Body not orange, and without white splotches on the dorsum 5
5a Cerata smooth, each bordered by a white line; body usually whitish, translucent (some specimens are mauve, and occasionally the cerata are pinkish); with white lines around the edge of the foot and oral veil, as well as between the rhinophores Dirona albolineata
5b Cerata usually roughened, each with a pale red spot, but not bordered by a white line; body light brown to greenish gray, with small yellowish, greenish, and pink dots; without white lines around the edge of the foot and oral veil, or between the rhinophores (not likely to be found north of Oregon) Dirona picta
Lower Taxonomic Levels Covered in This Key:

  Armina californica
  Dirona albolineata
  Dirona pellucida

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