146 Prof. G. J. Allman on the Anatomy 0/ Actseon. 



Action, 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- 

 taenia two, auriform, not retractile. Anus lateral, placed at the 

 right side. 



A. viridis (PI. V. figs. 1, 3, 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 points 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. TJie 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 their 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 sm-faces 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. Cy with membranous walls leads beneath a slightly bifid 

 lip (PI. V. fig. 3.) to an irregularly spherical body, PL VI. a, which 

 consists of thick walls inclosing a central cavity. In this body 

 is contained a tongue of very singular structure, PL VI. b 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 



