UNIVALVES. 



PLATE XV. 



Gems. HELIX. 

 Character. Shell slightly spiral ; the body and mouth very much rounded, orbi- 

 culated, the outside rim of the mouth ending at the umbilicus, which stands under- 

 neath ; part of the body naked, and without a columella, projecting into the mouth, 

 having no beak. 



Species. 

 No. 1. Helix pictoria. Shell richly striped with brown, blue, and yellow; the 



mouth brown, and circularly formed. 

 No. 2. Helix grisea. Shell gray, striped with purple bands, variegated; one of 



the folds of the spire orange colour ; mouth white. From a shell in the 



British Museum. Native place unknown. 

 No. 3. Helix cincta. Shell striped with red and white ; spire yellow ; mouth 



gray, slightly quadrated. 

 No. 4. Helix colubrina. Shell yellow, streaked red, with a small pattern like 



a half moon, or the back of a snake ; mouth brown. A native of the 



Mediterranean Sea, and rather rare. 

 No. 5. Helix subviridis. Shell striped with different bands of green ; mouth 



purple ; the spire slightly pointed. From the coast of New Zealand. 



Genus. STRIGULA. 

 Character. Shell spiral, tapering in the spire, having no beak ; round at the bot- 

 tom ; the mouth very narrow and oblong, having a rim all round, with strong and 

 prominent teeth, projecting inwardly and variously. 



Species. 

 No. 1. Strigula ornata. Shell of a pale green, shaded ornamentally with brown 



streaks; rim of the mouth white, the inside of a rich brown. This shell 



is very rare, and found only in the Southern Ocean. 

 No. 2. Strigula fusiformis. Shell red, richly spotted with black wavy spots, 



forming a singular and striking pattern ; the mouth brown, with a white 



rim. Native place unknown. 

 No. 3. Strigula maculata. Shell pale mottled red, closely spotted with black 



marks ; mouth of dark brown, and the rim white. From a shell in the Col- 

 lection of the Author. 

 No. 4. Strigula purpurea. Shell wholly purple, except the mouth and rim, 



which are of a warm brown colour. 



REMARKS. 

 The genus Helix will be readily distinguished by the circumstance of the rim running only 

 round a part of the mouth, which distinguishes it from the Pomacea. These shells are gene- 

 rally very thin in their texture ; they are found in fresh-water rivers, and on dry land ; a con- 

 siderable variety of them are found even in England. The Strigula is distinguished from 

 the other shells of a similar form by a very narrow twisting mouth, having teeth on each 

 side, and, like the Helix, is very thin in the texture of its substance. From the resemblance 

 which the shells of this genus bear to a mouth armed with teeth, they have sometimes been 

 denominated the Grinning shells ; the internal structure must be rather curious, for they are 

 generally flattened from front to back, like the Biplex, before described, and of course con- 

 sidered as deviating from the common form of circular-bodied shells, which chiefly predo- 

 minate in nature. 



