165 



of South America, West Indies, India, and China, and are of sluggish 

 habits, crawling and burrowing into beds of wet sand and mud. 



1. agriensis, Recluz. 12. 



2. Antillarum, id. 13. 



3. apertus, Anton. 14. 



4. bifasciatus, Recluz. 15. 



5. Carolius, Chenu. 16. 



6. clathratus, Bosc. 17. 



7. concavus, Lam. 18. 



8. Cuvierianus, Recluz. 19. 



9. Delessertii, Chenu. 20. 



10. depressus, Phil. 21. 



11. Deshayesianus, Recluz. 



Species. 



haliotoideus, Linn. 22, 



insculptus, Ad. $f Rv. 23 



Italicus, Chenu. 24 



Javanicus, id. 25, 



lacteus, Klein. 26 



lasvigatus, Lam. 27 

 latifasciatus, Ad.^-Rv. 28 



Leacliii, Blainville. 29. 



Levesquei, Recluz. 30 



Listeri, Recluz. 31 



maculatus, Say. 

 neritoideus, Linn. 

 perspectivus, Say. 

 Petitianus, Recluz. 

 planulatus, Chenu. 

 sinuatus, Recluz. 

 striatellus, id. 

 striatus, Be Serr. 

 Tuvonicus, Recluz. 

 zonalis, Quoy. 



Figure. 



Sigauetus concavus. PL 1. Shell, with animal, showing its capacious 

 hooded hinder lobe, and acuminately folded front lobe, from which 

 protrudes one of the tentacles belonging to the head concealed be- 

 neath. — From M. aVOrbigny's ' Voyage dans I'Amerique Meridionale.' 



Sigaretus concavus. PI. 23. Pig. 137. Shell of the same species divested of 

 the soft parts, showing its thin, arched columella and inflated aperture. 



Family 1 1 . PERISTOM ATA. 



Shell ; globose or turbinated, sometimes discoid, with little sculp- 

 ture beyond a malleated or indented surface or an occasional 

 keel, mostly of a sombre olive or greenish colour. 



This small family includes the freshwater pectinate-gilled gastropods, 

 in which the shell is mostly of a round or roundly-turbinated snail-like 

 form. The largest are the Ampullarice, whose shells are stoutly globose 

 and inflated. They inhabit chiefly the banks of rivers, in parts liable to 

 be dried up for a season, and to meet the exigences of this change of 

 condition are furnished with a double system of respiration, a water- 

 breathing and an air-breathing apparatus. The next group in the family 

 are the Paludina, which are smaller and more numerous, but still of the 

 same dark, sombre character, enveloped in a horny epidermis. Lastly 



