74 REPORT—1843. 
Ferussac’s variety 6. The only British species with which it can be compared as 
to form is L. Sowerbii, In some districts of Ireland the species is not uncommon, 
fréquenting gardens and thick herbage. 
In the course of the paper all the British Limaces were mentioned as occurring in 
Ireland, with the exception of Limax brunneus (Draparnaud), which had not as yet 
come under the notice of the author. 

Prof. Forbes exhibited several living animals which he had taken by means of the 
dredge off the coast of Cork. Some of these were but rarely taken; amongst them 
were a white variety of Cyprea nattica, Ophiura texturata, Buccinum reticulatum, 
Ophiotoma roseola, several species of corallines and various crustacea, and specimens 
of the genus Polycera, Eurastia, Trochus, and a hermit crab. 

Prof. Forbes exhibited specimens of animals which had been dredged up on the 
coast of Ireland by Mr. Hoskyn, R.N. He then read a communication from Mr. Alder, 
describing a new species of molluse found at Dalkey Island, near Dublin, having a 
shell in all respects similar to that of the genus Rissoa, from which, nevertheless, the 
animal differs materially, The most striking peculiarities were the presence of four 
tentacula, and the position of the eyes, which are placed on the back, at some distance 
behind tlie tentacula, and not at their base, as in Rissoa and the allied genera. 

On Plumatella repens. By Dr. Atiman. 
The author divided his paper into two sections, in the first of which he gave the 
zoological characters of the Zoophyte, and in the second entered into the zootomical 
details of its structure. In the first part of the paper it was attempted to reduce to 
some sort of order the chaotic mass of synonyms. with which the zoophyte in ques- 
tion was encumbered. This was facilitated by keeping in mind the existence of two 
variations which Plumatella repens is seen to assume. In one of these the zoophyte 
will be found attaching itself to flat surfaces, as the under side of stones, and of the 
floating leaves of water plants, &c., being closely adherent in its entire extent. In 
the second variation it will be found fixed to surfaces of small extent, as submerged 
stems and pieces of stick, and as the animal continues to develope, the branches 
having no extensive surface of attachment will become free, and a more or less en« 
tangled bushy mass will be the result. 
Plumatella repens exhibits in a high degree of perfection the molluscan type of 
structure, and a distinct pharynx, stomach and intestine may easily be traced. Con- 
nected with the mouth, there is here, as well as in most other freshwater zoophytes of 
the same order, a very singular valve-like organ. This is situated between the mouth 
and the inner margin of the crescentic tentacular disc. Its form is somewhat that of 
the epiglottis in certain animals ; it is convex towards the mouth, concave on the op- 
posite surface. That surface which looks towards the mouth is covered with cilia, and 
to the other there is attached a sacciform membrane. The orifice of this sac cor- 
responds with all the posterior surface of the valve, and to that portion of the tenta- 
cular disc which lies between the latter and the concavity of the crescent, and is thus 
completely closed, except at a small orifice in the disc, by means of which the sac 
of the valve would appear to communicate with the space between the body of the 
polype and the reflected tunic, and through this with the general cavity of the polype 
cell. The motion of the valve consists in a depression of this organ towards the 
mouth, followed bya return to its original position ; and a rapid succession of these 
movements may frequently be observed. It is difficult to say by what mechanism the 
motion of the valve is effected, but it is very probable that it is the result of the in- 
jection of the sac with fluid through the opening in the disc. 
The crown of tentacula is surrounded at its base by a caliciform membrane of 
extreme delicacy and transparency. This calyx is adherent to the tentacula for a 
short distance from their origin, but near its edge it becomes free, and hangs in loose 
plice from their sides. 
The pharynx opens into the stomach by a distinct papilliform projection, which be- 
comes prominent during deglutition, That part of the stomach which receives the 
pharynx consists of a remarkable elongation, occupying the place of the gizzard in 
many other zoophytes of this order, but in the present species not differing in struc- 

