126 CUMANOTUS BEAUMONTI.
part of the body had been lost, as it ends abruptly only 3-^4 mm. behind the heart.1
The outline of the anterior end of the foot is like Eolis nana, except that the sides are
produced into small angular projections kept tuckëd in and consequently inconspicuous.
Head nearly as wide as the foot. Thé oral tentacles very minute; merely short processes
of angles of the oral veil. The rhinophores are long and smooth, held erect with tips
bent back. The eyes do not show. Papillaa very numerous and extremely long, slender
and tapering to fine points, constantly in motion, curling and uncurling, and when at rest
convoluted. A group of small papilla, apparently three rows, is wholly in front of the
rhinophores on each side. Then a row on each side abreast of rhinophores. Another
row between this and the next, which is abreast of the anterior end of the heart. Then
a row level with the posterior end of the heart. The outer ends of the rows are not
double.
“ The colour of the body is red, tending to orange on the rhinophores, but elsewhere
more rosy. The colour seems to be situate in the superficial tissues. The papillaa are
superficially flesh-coloured. The hepatic caeca are in most of the papillae rosy purple
throughout, but in a few pale greenish purple, except at the tip, which is rosy purple in
all and more deeply coloured than the rest of the organ. The caeca are slender, especially
at the distal ends, and much corrugated. The extreme tips of the papillae beyond the
end of the caaca are yellowish flesh colour, deeper than the superficial colour of the rest
of the papillae.”
I have examined two preserved specimens given me , by Mr. Beaumont, 20 mm. and
14 mm. long respectively. The colour is dead white, not very transparent. The hepatic
diverticula in the cerata are yellowish white and corrugated. The external characters
agree with Mr. Beaumont’s description. The front of the foot is broad and expanded, but
the tentacular angles are small and bent downwards and inwards. The anterior margin
is not grooved. Over the mouth is a broad oral veil (5'3 mm.) expanded into short
tentacles (1*7 mm.) at the sides. The rhinophores are long (7*5 mm.), thin, not
perfoliate, and placed close together on a slight prominence. There are three rows of
cerata distinctly in front of them. The cerata are set on eight narrow, curved ridges,
which are single and do not form horseshoes. The first three rows are close together,
the next three not far apart, but the last two are more distant. In the perfect specimens
the length of the cerata obscures this arrangement. There are four to six cerata in each
row. The cerata in front of the rhinophores are short, cylindrical, and 2—4 mm. long.
The posterior cerata are very long; in the specimen, which has a body 20 mm. long, they
measure as much as 15 mm. and are about 1 mm. broad at the base.
The jaws bear two or three rows of denticles. The radula is triseriate, and consists
of twenty and fourteen rows respectively in the two specimens. The central tooth has a
strong central cusp, which bends slightly downwards, and hence sometimes appears asymmetrical
when pressed flat in a slide. On each side of it are a number of small denticles
of varying shape and size. The smallest number observed was sixteen and the largest
twenty-four. The laterals are also broad, with slightly lower cusps, and twenty to thirty
accessory denticles on the inner side. No denticles were visible on the outer side of the
laterals. The female orifice is dilated into a bursa copulatrix. The upper and lower
1 The specimens here described are much the same.
CUMANOTUS BEAUMONTI. 127
margins of the entrance are each armed with a circular or elliptical pad, which bears
round its margin twelve conical tubercles terminating in hooks. They appear not to be
hard or chitinous (fig. 5).
The penis, which is partially protruded in one specimen, is sickle-shaped and very
deeply grooved, consisting of a lamina folded down the middle and probably capable of
assuming a foliaceous expansion. It is unarmed. The spermatotheca is large and
spherical.
With respect to the function of these pads Mr. L. R. Crawshay writes to me from the
Plymouth Laboratory, where he watched the movements of Cumanotus in the tanks, that
what was observed points strongly to the conclusion that they are really ? clasping
organs. “ If the organs of the one individual are called A (<?), B( ? ) , and of the other,
X (<J), Y (?), what was observed was as follows: The two individuals were placed
right to right with the complete apparatus of both extended and approximating. The
base of A (<J) was grasped laterally by an upward extension (i. e. presumably the
pads) on both sides of Y ( ? ), and the base .of X ( <J ) was similarly grasped by upward
lateral extensions of B ( ? ). In each case a sort of peristaltic movement on the part of
B ( ? ) and Y ( ? ) occurred. As the grasp of B ( ? ) and Y ( ? ) extensions relaxed, the
flow of spermatozoa from X ( <J ) and A (<? ) respectively was distinctly visible, while as
the grasp of the extensions closed round the base of X (<?) and A ( <J )> the flow of
spermatozoa was checked.” As far as I am aware, a female clasping organ of this kind
has not yet been recorded among Nudibranchs, but it is possible that in some other genera
of Solids its nature may have been misunderstood.
The spawn consists of a short spiral coiled about six times and suspended by a
thread (fig. 4).
I t is doubtful whether Cumanotus beaumonti and Cumanotus laticeps are specifically
the same. The identity is not improbable, but Odhner’s specimens (judging from the
figures) had lost all the cerata. Cumanotus beaumonti is remarkable for having a short
truncated body and extremely long snaky cerata, but when these have fallen off the
Plymouth specimens look very like Odhner’s figures, and have the margin of the foot
similarly expanded. There may also be differences in the denticulation of the jaws and
lateral teeth. But these are slight divergences, and hardly of specific value unless
associated with others. Still, until a complete specimen of the Norwegian form has been
examined it is safer not to unite the two species, and provisionally I think the genus may
be tabulated as follows:
Cumanotus Odhner, 1907.
1. G. beaumonti (Eliot), 1906.
2. C. laticeps Odhner, 1907.
If the species are united the name beaumonti has priority.
C. laticeps is known by four specimens obtained at Sorvaar, in the extreme north of
Norway, in 5—10 fathoms of water. C. beaumonti has been captured at Plymouth, twice
in Barn Pool, and on several occasions in Jennycliffe Bay, at a depth of 2—5 fathoms, and
though far from common, appears to be a resident and not merely a visitor.