148 TERRESTRIAL AIR-BREATHING MOLLUSKS. 



the alternate undulating expansions and contractions of the locomotive band 

 of the foot are seen to take place in the same manner as when they are in 

 motion on a plane surface. 



This species is much more prolific than the others, the number of eggs de- 

 posited during the year being sometimes several hundred ; its numbers, in 

 favorable localities, are therefore very great. It begins to lay its eggs early in 

 the spring, and continues, with intervals, until checked by the cold of approach- 

 ing winter. The last deposit of them often remains in the soil until the suc- 

 ceeding spring, when they are hatched with the first generation of the year. 

 The eggs are semi-transparent, and nearly globular. They produce young in 

 about twenty days after they have been deposited. 



M. Bouchard-Chantereaux has observed them to deposit eggs in sixty-six 

 days after their own birth, and to attain their full size in eighty-two days. 



This species varies very much in color, and the descriptions by different 

 authors, being drawn principally from it, differ greatly from each other ; but 

 whatever may be the color, the peculiar character of the furrows and the tuber- 

 cles remains constant. In a state of contraction the back is arched; the head 

 is entirely withdrawn under the mantle ; the glands of the skin are very promi- 

 nent, making the surface appear rough ; the carina is more apparent ; and the 

 posterior extremity, being a little turned to one side, appears to be oblique. It 

 is described by some authors as constantly oblique, but the obliquity disappears 

 when the animal is fully extended. When in motion, the head extends consid- 

 erably beyond the mantle, and there is an interval between its margin and the 

 base of the eye-peduncles equal to the length of the tentacles. The mantle 

 adheres to the body by its posterior central portion, and it is in this part of it 

 that is found imbedded the testaceous rudiment, or shell. This is oval, curved 

 above, very thin and delicate, having a transparent epidermis. At its posterior 

 part there is a slight apical prominence, and the appearance of indistinct con- 

 centric lines of growth. 



There is no considerable variation in the species except in regard to color, 

 which varies almost infinitely. 



Jaw wide, low, slightly arcuate, with broad median projection. 



Limax agrestis^ (PI. I. Fig. H) has about 50 — 1 — 50 teeth on its lingual mem- 

 brane, with 18 perfect laterals. The centrals have a much more graceful out- 

 line to the reflection than in the two last-named species. The median cusp is 

 longer and more slender, with a more slender cutting point ; the subobsolete 

 side cusps are more marked, and bear well-developed, triangular, slightly 

 curved cutting points. The lateral teeth are like the centrals, but unsymmet- 

 rical by the suppression of the inner lateral lower expansion of the base of 

 attachment. There is, however, an inner cutting point lying against the inner 



1 The figure given of the marginals of L. agreslis by Lindstrtim (Gotlands nutida 

 Mollusker, PI. I. Fig. 3) disagrees with my observation by the bifurcation of the 

 marginals. 



