es 
ae 
298  Prof.G.J.Allman on a new Genus of Gasteropods. 
cond is occasionally met with ; it is characterized by the spots 
being of a pure white. 2 i 
Geomalacus is at once distinguished from Arion (to which how- 
ever it appears to approach more nearly than to Limaz) by the 
position of the generative aperture, this orifice being placed in 
Arion just below the entrance to the respiratory chamber, while 
in Geomalacus its position is similar to that in Limaz, bemg just 
behind the base of the smaller tentaculum of the right side. The 
presence of a solid testaceous rudiment may be placed in con- 
junction with the last as a character distinguishing it from Arion ; 
though upon this, viewed isolatedly, much stress should not per- 
haps be laid, as im the last-named genus the rudimental shell 
would appear sometimes to assume a considerable degree of so- 
lidity. From Limaz the distinction is well-marked, bemg found 
in the presence of a caudal muciferous follicle, and in the posi- 
tion of the respiratory orifice anterior to the centre of the lateral 
margin of the shield ; the total absence of a dorsal keel also is a 
character by which Geomalacus resembles Arion rather than Li- 
max. 
The habits of our mollusk are somewhat curious. It possesses 
a singular power of elongating itself so as at times to assume the 
appearance of aworm. By this means it can insinuate itself into 
apertures which we could scarcely conceive it possible for it to 
enter. This curious property indeed was very nearly the cause 
of my losing the first, and at the time the only specimen I had 
seen. I had placed the mollusk, as I supposed, securely in a 
botanical collecting-box, when to my surprise I found shortly after 
that it had transgressed the limits I had assigned it. The erea- 
_ ture not liking its confinement had insinuated itself beneath the 
lid, which not closing very perfectly had afforded for its escape a 
fissure of about a line in width. I was fortunately in time to 
recapture my prisoner, and the knowledge which I had thus 
gained of its habits suggested a stronger prison for the future, 
I have since been favoured by Mr. Andrews with numerous 
very fine healthy specimens from the original locality, where the 
mollusk is abundant, and beyond which it has not as yet been 
detected. In an interesting letter which I have received from 
this gentleman is a highly graphic deseription of Geomalacus 
among its native rocks. From Mr. Andrews’s letter I eannot do 
better than select the following extract as a conclusion to the 
present notice :-— 
‘Lake, or Loe Carogh, lies to the south of Castlemain Bay, 
in the county of Kerry, and stretches nearly north and south five 
miles. The lake narrows at the centre, where huge cliffs (prin- 
cipally of the old-red sandstone group) rise precipitously from 
the margin on either side to a great height. On the east side 
