GASTEROPODA. 109 



above, white beneath. Inhabits gardens in Britain and 

 France. 



Genus 4.— FARM ACELL A.— Lamarck. 



Generic Character. — Body creeping, oblong; middle of 

 the back moderately convex, and shield-shaped; the hind 

 part in the form of a tail, laterally compressed, and acute 

 above ; shield ovate, fleshy, adhering at its posterior part, 

 and free before, enveloping a shell, and having a notch in 

 the centre of its right margin ; four tentacula, the two pos- 

 terior the largest; respiratory and anal orifices under the 

 notch of the shield, and the orifice for generation placed 

 between the two tentacula of the right side. 



Parmacella calyculata. — The Cdp-shaped Parma- 

 CELLA. Plate XIII. fig. 31. Ovate; left margin broad 

 and reflected, right margin reflected at top and acute be- 

 neath ; exceedingly thin, transparent, and of a pale yellow- 

 ish-brown. 



Genus 5.— ONCHIDIUM.— Zawarc/^. 



Generic Character. — Body oblong, creeping, marginated 

 on all sides ; head projecting, the lower part with a promi- 

 nent margin; two rectractile, cylindrical tentacula; two 

 auriform appendages at the sides of the mouth, which is 

 destitute of maxillary processes; the respiratory and anal 

 orifices distinct, placed under the posterior extremity of the 

 body. Destitute of a shell. 

 Annals du Museum, vol. v., p. 38, plate 6. 



Section II. — Hydrobranchi^. 



The branchiae formed of filaments or laminae, and pecti- 

 nated or tufted. The animals respire in water. 



TRIBE II. LAPLTSIACEA. 



The branchiae placed in a particular cavity, situated near 

 the posterior region of the back, and covered by an oper- 

 cular shield ; the animals possessing tentacula. 



K 



