MOLLUSC A. 
411 
Genus 68.—LUTE A.— Brown. 
Generic Character —Shell globular; spire short, subacute; 
aperture ovate ; outer lip not continuous, slightly inflected at 
top, and acute at the base; a little reflected on the base of the 
columella, and subumbilicate. 
Lutea lacuna — The Ditch Lute a. 
Plate LXXXVI. fig. 10. 
Very diaphanous, slightly wrinkled, and of a greenish horn- 
colour. Half an inch long. Inhabits the ditches in Britain. 
Genus 69. — PLANOKBIS. — Lamarck. 
Generic Character .—Shell discoid; spire depressed; the 
volutions apparent on both sides; aperture oblong, luniform ; 
axis of shell remote; margin not reflected; destitute of an 
operculum. 
Planorhis carinatus. — The Keeled Planorbis. 
Plate LXXXVI. fig. 11. 
Depressed ; upper side concave, with a keel round the middle 
of the body. Three-fourths of an inch in diameter. Inhabits 
the ditches and lakes of Europe. 
Genus 70. — PLANARIA.— Brown. 
Generic Character. — Shell discoid, depressed on both sides ; 
the volutions conspicuous on either side ; spire slightly produced 
above, and concave beneath ; aperture ovate; edges of outer lip 
acute ; destitute of an operculum. 
Planar ia alba .— The White Planaria. 
Plate LXXXVI. fig. 17. 
White, slightly wrinkled transversely; outer lip with a nar¬ 
row margin behind. One-fourth of an inch in diameter. 
Inhabits the coast of Dunbar,— Scotland. 
TRIBE X.-COLIMACEA. 
Spiral, but without any exterior projections, except the ad¬ 
ditions of growth; outer lip frequently reflected ; terrestrial 
tentaculee of the animal cylindrical, and devoid of an operculum. 
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