A7iimal of Helicolimax Lamarckii. 339 



posterior half of what appeared before to constitute a uniform tumid 

 cuirass. Through this opening appears the shell, the back part of whose 

 last volution, as the animal becomes more and more dry, is gradually 

 more exposed by the enlargement of the sinus which dilates more par- 

 ticularly on the left side ; till finally the whole shell is exposed, with the 

 exception of about a line's breadth of the outer lip covered by a narrow 

 portion of the cuirass like a border, which becoming broader towards the 

 right side, extends backwards towards and partly over the spire in a kind 

 of broad lateral lobe. The animal is even sometimes completely retracted 

 within the shell, like a Helix ; and had I not observed in the same indi- 

 viduals the whole process of transition, from the aspect of a Limax with- 

 out the slightest appearance of external shell to that of a Helix completely 

 contained within one, the identity of the individuals in the two states 

 would have seemed most questionable. ,^ / 



The shell is placed with its spire posterior and directed towards the 

 right side. Its posterior spiral part is sunk into a kind of hollow bed 

 whose margins rise around and closely embrace it. When partially 

 exposed, it may even be raised up out of this sort of sunken bed, formed 

 for its reception, by something applied behind to its spire. The margins 

 which embrace it originate on each side of the body just below the edge 

 of the cuirass, as far back as the respiratory orifice, becoming higher or 

 broader posteriorly. They are elevated, sharp-edged, with oblique 

 grooves or strim dividing them into tumid compartments, and are highest 

 or broadest close beneath, L e. behind, the spire, where they leave a small 

 triangular hollow or cavity, and then approaching close together, form 

 by their opposition a keel which runs some way down the middle of the 

 posterior extremity. 



The respiratory orifice is on the right side, within a large distinct sinus 

 on the edge of the cuirass near its posterior end, i. e, just beneath the spire 

 of the shell, but a little before it; so that on looking into the orifice, the 

 shefl is seen distinctly forming a roof to the pulmonary cavity. It is 

 lined with a tissue of ramifying vessels, whose main branch, proceeding 

 from a whitish internal organ situated backwards towards the spire and on 

 the left side (the slime-organ, or "Sac de la viscosite," Cuv.?), runs for- 

 wards in an oblique direction across the shell tov^rards the head of the 

 animal. These vessels are best seen externally through the substance of 



