ARION INTERMEDIUS. 241 
INTERNALLY, its organization bears, according to Simroth, most resemb- 
lance to that of Arvon subfuscus, but is more simple and primitive. 
Perhaps the most sharply-marked difference is in the character of the 
mandible or jaw, which is very delicate, and displays a few exceedingly 
wide but only slightly convex ribs on its anterior surface. 
Original Description.—Lima« intermedius. Animal gris-jaundtre pale. Ex- 
trémités surtout la postérieure, @un beau jaune Vor. Cotes blanchatres, marqués 
antérieurement de quelques petits points noirs, un peu espaceés en ligne pres du bord 
du pied. Tete, cou et tentacules gris-foneé ou noiratres. Plan locomoteur granu- 
leux. Mueus jaune. Limacelle blanche, opaque et rugueuse. Long. de Panimal, 
15 & 20 mill.— NORMAND, Descr. Six Limac. Nouv., 1852, p. 6. 
Description. —ANIMAL small but plumply built, about twenty or more mill. long 
when extended, and about three-and-a-half mill. broad; of a very pale yellowish 
ervey or almost white, with or without a broad and dusky but ill-defined mid-dorsal 
streak, shading off downwards ; ancestral lateral band on each side of the body, 
same shade as the back, shading off below to the yellowish-grey foot-fringe ; 
SHIELD finely granulose, rounded at both ends, about one-third the length of the 
body, usually of a yellowish-tint, especially anteriorly, with pale dusky ill-defined 
mid-patch and lateral bands which meet behind ; RESPIRATORY ORIFICE almost 
median, but the GENITAL APERTURE is nearly mid-way between the pulmonary 
orifice and base of right ommatophore, but below both ; BODY TUBERCLES shortly 
polygonal and somewhat prominent, and in certain postures of the anjmal appear 
keeled, but under a lens the tubercles are seen to be surmounted by short white 
glandular spikes, which seem capable of individual movement, and whose erection 
appears dependent upon the will or emotion of the animal ; when removed from its 
accustomed environment, placed on the hand, or during extension, all rugosity 
may disappear, and the skin appears smooth and shining, but the loosely implanted 
glandular crests give it the aspect of being dusted with flour; HEAD and NECK 
darker than DORSUM ; CAUDAL GLAND conspicuous ; TENTACLES small ; FOOT-SOLE 
yellowish and undivided, the lateral areas yellow with slime, which also accumn- 
lates at the caudal end of the animal as well as on the anterior part of the shield ; 
FOOT-FRINGE yellowish-grey, not visibly lineolate. 
SHELL in British specimens usually represented by a thin and indistinct layer of 
limey-paste within the shell-sac, whose inner walls are densely speckled with lime- 
cells, although scarcely any free particles can be discerned. Normand and the Italian 
authors, however, describe the vestigial shells as white, opaque, and solid. 
INTERNALLY, the walls of the ecelom are white and very thick for so small an 
animal, much thicker than in A. eireuwmscriptus ; the HEART, KIDNEY, and LUNG 
cavity are conformable with the generic character; the AORTA divides late, and is 
broad and white with lime particles, but there are no lime-charged hepatic arteries, 
such as form the beautiful white and lace-like tracery in dA. afer; the lateral 
SINUSES of the ccelom are conspicuous, and correspond in position with the exterior 
lateral bands ; the SUPRA-PEDAL GLAND is well imbedded in the tissues, and not 
more than half the length of the sole ; the CEREBRAL GANGLIA with short commis- 
sures, which shew no signs of lime; the PEDAL GANGLIA are the largest and the 
most conspicuous of the SUB-CESOPHAGEAL group, while the BUCCAL pair are as 
usual separated by about their own diameters. 
The CEPHALIC RETRACTORS are of the true 
Arion character. The two TENTACULAR muscles 
arise, about three mill. apart, from the under- 
surface of the posterior part of the mantle, the 
right one furthest back, as usual; they are flat, 
with very broad, fan-shaped roots, each divides ot A. snderiibanns 
early for the upper and lower tentacles; the Normand x 3. 
PHARYNGEAL retractor arises further back, pos- \ | D (Raheny, Co. 
Zs A ublin, Dr. R. F. 
terior to the mantle and nearly mid-dorsally, but Scharf), 
inclined to the right side, it is much slenderer 
than the tentaenlar muscles, and forks a little ji 
later than half-way. 
The ALIMENTARY SYSTEM has the G:SOPHAGUS pigmented and partially fused 
with the PHARYNX, as is usual in the genus, but so much so that the parts have to 
be torn up to display the BUCCAL GANGLIA. The INTESTINAL CANAL is triodromous 
and the details of its arrangement and the amount of torsion or twisting it has 
10/12/05 Q 
Fic. 243.— 
Cephalic retractors 
