Hawaiian Opisthobranchiates — OsTERGAARD 
folds; shell present or absent in the adult 
(suborders Tectibranchiata and Ascog- 
lossa) 2 
Respiratory organs consisting of a circle 
of gills surrounding the anal papilla, or 
of branchial processes covering the body; 
shell and mantle absent in the adult 
(suborder Nudibranchiata) 10 
2(1). Shell more or less conspicuous and 
generally covering mantle and gills ... 3 
Shell absent in adult; respiratory folds, 
when present, not in the form of gills . . 9 
3(2). Gills on dorsal side of body, usually 
covered by shell or mantle 4 
Gill consisting of a plume on right side 
of body Pleurobranchus 
4(3). Shell large and almost capable of con- 
cealing the animal 5 
Shell rudimentary and nearly or entirely 
concealed from view 7 
5(4). Parapodial lobes extending the whole 
length of animal Hydatina 
Parapodial lobes covering anterior part 
of shell 6 
6(5). Shield extending from foot to cover 
posterior part of shell. .... Haminoea 
No shield covering posterior part of foot 
Atys 
7(4). Shell and mantle covering gills be- 
tween parapodial lobes .8 
Shell and mantle rudimentary or absent 
Notarchus 
8(7). Shell hatchet- shaped; body of animal 
tapering anteriorly and obliquely trun- 
cate posteriorly. . . Dolabella 
Shell somewhat oval in outline; body of 
animal slender and fusiform. . . .Tethys 
9(2). Parapodial lobes united dorsally by 
regular margins; their inner surfaces cov- 
111 
ered with longitudinal narrow branchial 
folds supporting commensal algae 
Placobranchus 
Parapodial lobes with folded margins not 
fully united dorsally; no branchial folds 
present Elysia 
10(1). Respiratory organs consisting of a 
circle of gills surrounding anal papilla . 1 1 
Respiratory organs consisting of bran- 
chial processes covering the body. . . 13 
11(10): Cloak of great lateral spread and 
produced into swimming lobes folded 
on the sides when the animal is at rest 
. Hexabranchus 
Cloak narrow and not used as swimming 
lobes, nor folded when the animal is at 
rest 12 
12(11). Body slender, bluish white with in- 
terrupted blue striae. Gills simple pinnae, 
white, with bands of orange. ......... 
Glossodoris 
Body elongate, about one third as wide 
as long, bluish black with fine white 
specks. Gills with long lateral branches 
Doridopsis 
13(10). Body broad anteriorly, tapering pos- 
teriorly and covered with numerous 
slender branchial papillae. Rhinophores 
and oral tentacles simple Aeolidia. 
Body slender, fusiform, beset with two 
rows of broad branchial processes. Rhin- 
ophores placed on dorsal side of an ex- 
tensive oral veil Melibe 
CLASSIFICATION OF SPECIES CONSIDERED 
Suborder Tectibranchiata 
Family Scaphandridae 
Genus Atys 
(A. semistriata ) 
Family Akeridae 
Genus Haminoea 
(H. crocata) 
