ARION INTERMKDIUS. 241 



Internally, its organization bears, according to Simroth, most resemb- 

 lance tij that of Avion subfuscus, but is more simple and primitive. 

 Perliaj)s tlie 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. — Limax iiifa-incdiiif:. Animal giis-jauniltve pale. Ex- 

 triniites surtout la po.st6rieure, d'un beau jaune d'ov. Coles blancltatre.s, marqu^.i 

 aufc^rieurement de quelques petits points noivs, un pea espac^s en ligne pies dn liord 

 du pied. Tete, cou et tentacules gris-fonce ou uoii'iltres. Plan locomoteur granu- 

 leux. Mucus jaune. Liraacelle blanche, opaque et rugueuse. Long, de I'aninial, 

 15 a '20 mill.— NOKMAND, De.scr. Six Limac. Nouv., l%o'l, 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 

 grey 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 oft' 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 ; respiratoky 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 animal appear 

 keeled, but under a lens the tubercles are seen to be surmounted by short wliite 

 glandular spikes, which seem capable of individual movement, and whose erection 

 appears dependent upon tlie will or emotion of the animal ; when removed from its 

 accustomed environment, placed on the hand, or during extension, all rugosity 

 may disappear, and tlie skin appears smooth and shining, but the loosely implanted 

 glandular crests give it tlie aspect of being dusted with Hour ; head and xeck 

 darker than dorsum ; CAUDAL GLAND conspicuous ; TENTACLES small ; FOOT-SOLE 

 yellowish and undivided, the lateral areas yellow with slime, which also accumu- 

 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. Noi'inand and the Italian 

 authors, however, describe the vestigial shells as white, opaque, and solid. 



Internally, the walls of the coelom are white and very thick for so small an 

 animal, much thicker than in A. circum'icriptuK ; the he.\rt, kiiiney, and lung 

 cavity are conformable with tlie generic character; the aorta divides late, and is 

 broad and while with lime particles, but there are no lime-charged liepatic arteries, 

 sueli as form the beautiful white and lace-like tracery in ^-1. ater ; the lateral 

 SINUSES of the cadom are conspicuous, and correspond in position with ihe 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 sheM- no signs of lime ; the pedal ganglia are the largest and the 

 most conspicuous of the sub-(ESOPHAGEAL group, while the buccal jiair are as 

 usual separated by about their own diameters. 



The cephalic retractors are of the true ^ 



Arioti cliaracter. The two te\t.vculau muscles j 



arise, about three mill, apart, from the under- J 



surface of the posteiior part of the mantle, the M4 

 right one furthest back, as usual ; they are flat, /fj 

 with very broad, fan-shaped roots, each divides 1 



early for the upper and lower tentacles ; the 

 pharyngeal retractor arises further back, pos- 

 terior to the mantle and nearly mid-dorsally, but 

 inclined to the right side, it is much slenderer 

 than the tentacular mu.scles, and forks a little 

 later than half-way. 



The alimentary system has the oesophagus 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 



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