152 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY 
bark, becoming coarser toward the margin and heightening the radial effect 
of the whole. These lines serve to pick out smartly the rhinophore openings. 
In formol specimens the color becomes black, and in specimens cleared and 
viewed by transmitted light a coarse reticulation around the edge of the 
notaeum becomes very conspicuous especially posteriorly. Notaeum loose and 
amply covering all parts, often up-turned at the margin in life ; dorsal aspect, 
which in life is smooth, has a shagreen-like surface in preserved specimens from 
the calcareous particles of the integument. Foot rather long, bluntly tapered, 
anteriorly strongly cordate, posteriorly roundly pointed in life (in preserved 
material usually emarginate). Oral disc only as broad as foot, strongly con¬ 
vex anteriorly ; oral palps very thick and short. Rhinophores long (£ maxi¬ 
mum breadth of specimen), evenly tapered, covered for about half the length 
by a delicate white sheath. Entirely retractile together with sheath. Gills, 
which are most of the time hidden in living animals, lie posteriorly in the 
space between foot and notaeum, and consist of a set of simple overlapping- 
plates on each side of the cardiac vessel which unites them. These, together 
with the anal papilla which lies ventral and anterior to the heart in the median 
line, are only exposed in a few even of the preserved specimens. On the left 
side, just behind the neck, lies the genital opening from which the genitalia 
are usually everted in preserved material even when the animals were first 
stupefied with magnesium sulphate. In some sections through this sexual 
extrovert there appeared strongly-staining plumose structures at first suggest¬ 
ing gills and possibly representing a complicated armature of the penis but 
not positively identified by me. No signs of mandibular lamellae, or of the 
horny “Balken” described from the mouth cavity of Corambe, appear. .The 
radula is described supra. 
Unfortunately this inconspicuous little nudibranch, which occurred 
during August in fair numbers under stones on which Fucus was 
growing on the edge of swift water, and in dredgings of stones and 
weed from 2 fathoms, was at first taken for Doridella obscara Ver- 
rill (’73, pp. 400 and 664) and (’81-’82 p. 547) and therefore only 
casually studied and sketched in life. Consequently I am uncertain 
what is the exact structure of the rhinophore and sheath, but 
probably, as in Corambe, the sheath is longitudinally slit on its 
posterior (superior) face and the rhinophore itself is, for the pro¬ 
jecting portion, a sheet with the edges rolled inward posteriorly, 
as the comparison of my sections with Fischer’s (’91) very com¬ 
plete account of the anatomy of Corambe testudinaria makes it 
clear that almost all the structures bear some general resemblance 
to that species. As the animal, in which periods of considerable 
activity appear to alternate with periods of obstinate passivity, 
creeps on the under surface of the water the rhinophores are com¬ 
monly turned back in a graceful curve on each side. The gills are 
