MOLLUSCA. 
417 
phanous, slightly wrinkled, and of a pale straw-yellow colour. 
Inhabits gardens in Britain and France. 
Genus 4.—P A RMA CELL 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, en¬ 
veloping a shell, and having a notch in the centre of its right 
margin ; having four tentacula, the two posterior 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 calycutula. —The Cup-Shaped Parmacella. 
Plate LXXXVI. tig-. 31. 
Ovate ; left margin broad and reflected, right margin reflected 
at top and acute beneath; exceedingly thin, transparent, and of 
a pale yellowish-brown. 
Genus 5.—ONCHIDIUM.— Lamarck. 
Generic Character. —Body oblong, creeping, marginated on 
all sides; head projecting, the lower part with a prominent mar¬ 
gin ; two retractile, cylindrical tentacula ; two auriform appen¬ 
dages, nearly lateral; mouth underneath ; destitute of maxillary 
processes ; the respiratory and anal orifices distinct, placed un¬ 
der the extremity of the body. 
Section II. —Hydrobranchi.®. 
The branchiae formed in filaments or laminae, and pectinated 
or tufted. The animals respire in water. 
TRIBE II.-LAPLYSIACEA. 
The branchiae placed in a particular cavity, situated near the 
posterior region of the back, and covered by an opercular shield ; 
the animals possessing tentacula. 
Genus G. — DOLABELLA. — Lamarck. 
Generic Character. —Body creeping, oblong, narrowed in front, 
and posteriorly widened ; the area round, sloping, and obliquely 
