M \LACOZOA. GASTEROPODA. PULMOBRANCHIATA. 107 



The animal has the lower surface of the foot yellowish- 

 green, its margins greenish-yellow ; the broad bilohate flap 

 above the mouth greenish-yellow ; the tentacula of the same 

 colour, broad, thin, and broadly rounded ; the collar, or an- 

 terior induplicate fold of the mantle, yellowish-green anteriorly, 

 greenish-grey on the margin, grey variegated with black above ; 

 the body yellow, variegated with black, its hind part chiefly of 

 the latter colour, with the tip yellow. 



This species differs from any of the following, in having the 

 spire extremely small, although convex forming a minute 

 point or acuminatiori, or frequently truncate by decay or 

 erosion ; the shell so thin as to be semitransparent, or even so 

 clear that one can see an object through it, with fine regular 

 striae, but very seldom any longitudinal angular ridges on the 

 last turn ; the inside glassy. When it has lain dead for some 

 time, the shell becomes opaque, pale yellow externally, and 

 white within. 



Individuals of this species, shorter and broader than usual, 

 make a close approximation to Limnaeus auricularius. 



It occurs plentifully in the Loch of Skene, where I found it 

 on the 2d July, 1842 ; in pools of the Dee, on the 16th ; in a 

 mill pond near the base of the Hill of Fare, on the 30th, and 

 in various other localities. 



Limnaeus ovatus. Drap. Moll. Terr, et Fluv. 50. PI. 2. f. 30, 

 31. Lymnasa ovata. Lamk. Syst. vi. 2. 161 ; Ed. n. viii. 413. 

 Limneus pereger. Var. i. L. ovatus. Drap. Alder. Mag. Zool. and 

 Bot. i. 115. Limnseus pereger. Var. Gray's Turt. 234. Lim- 

 nea limosa. Flera. Brit. Anim. 274. Lymnaea ovata. Brown, 

 Illustr. PI. 42. f. 10, 11. 



B. Limncem pereger communis. Common Mud-Shell. 



Shell ovate, ventricose, very thin, brittle, semitransparent, 

 glossy with the spire short ; the aperture oval, acute behind, 

 three-fourths of the whole length ; the last turn oblique, dis- 

 tinctly striate transversely, generally marked with obscure 

 longitudinal ridges ; the colour pale brown, yellowish-brown, 

 or dull yellow. Length about nine-twelfths of an inch, breadth 

 five-twelfths. 



The animal has the head, foot, and lower surface of the 

 broad thin collar, greenish-grey, the upper or posterior sur- 

 face of the collar grey, variegated with black ; the rest of the 

 body blackish-brown, spotted with whitish-grey, or light 

 brown, the terminal portion umber-brown. 



The shell, when the animal is in it, appears of a dusky- 



