146 Prof. G. J. Allman on the Anatomy of Acteon. 
Acrmon, Oken, Aplysia, Mont., Aplysiopterus, Delle Chiaje, 
Elysia, Risso. 
Body subcylindrical, with two foliaceous lateral expansions 
which are produced beyond the posterior extremity of the body, 
where they unite with one another along the mesial line. Ten- 
tacula two, auriform, not retractile. Anus lateral, placed at the 
right side. 
“A, viridis (Pl. V. figs. 1, 2, 3.).—The largest specimens of A. 
viridis measured about nine lines in length ; the general colour 
of the body and foliaceous expansions is a dull green ; the latter 
are margined with purple and dotted on both sides ‘with small 
green, blue, and rose-coloured poits of a brilliant metallic lustre, 
and arranged in groups without any definite order ; similar dots 
are also found upon the upper surface of the body; a nearly co- 
lourless line extends from the posterior extremity of the body to 
the termination of the branchial expansions. The tentacula are 
of a dull purple, and the eyes are placed in the centre of a nearly 
colourless areola. The upper lip is dark purple. 
This little mollusk was obtained abundantly by means of a 
small dredge among Zostera marina in the harbours of Glandore, 
Castletownsend and Crook Haven, co. Cork, in the months of 
August and September 1844. 
When confined in a glass of sea-water it would creep upon the 
sides of the vessel, adhering not only by the under surface of the 
body, but by that of the lateral expansions along the whole 
length of thei junction in the mesial line ; external however to a 
narrow space corresponding to their line of junction, the expan- 
sions were entirely free, and possessed no power of attachment. 
Our little mollusk would also take delight in suspending itself in 
a horizontal position with its back downwards, from the surface 
of the water. It would sometimes separate its lateral expansions 
till they became placed nearly in the same plane, and again ele- 
vating them vertically, would bring their opposed surfaces nearly 
into contact. 
ANATOMY. 
Digestive system.—From a simple unarmed orifice in the an- 
terior extremity of the body, a short but rather wide canal, 
Pl. VI. c, with membranous walls leads beneath a slightly bifid 
lip (PL. V. fig. 3.) to an irregularly spherical body, Pl. VI. a, which 
consists of thick walls melosing a central cavity. In this body 
is contained a tongue of very singular structure, Pl. VI. 6 and 
PL. VII. fig. 5. It consists of a chain of hard transparent spines, 
and is curved so as nearly to return into itself, thus forming a 
loop, whose long diameter will be parallel to the axis of the buccal 
mass. M. de Quatrefages has given a correct figure of the organ 
as detached from the animal, but has overlooked a most singular 
