20V 



CHAPTER III. 



THE GASTEROPODA (concluded] AND PTEROPODA. 



Order 1. (concluded) (b) the Holostomata, or Entire-mouthed Sea Snails Family 8. NATICID.E 9. CANCELLARIAD^B 

 10. PYRAMIDELLID.E 11. SOLARIAD.E "The Staircase-Shell" 12. SCALARIAD.* Scalaria pretiosa, the " Wentle- 

 trap" Great Value attached to this Shell 13. CERITHIAD.E Potamides in Fresh Water 14. TURRITELLID.E 

 "Tower-shells" Vermetus "\Vorm-shells 15. MELANIAD.E 16. PALUDINID^E Fresh-water Snails the "Apple 

 Snail," Ampullaria Its Tenacity of Life 17. LITORINID.E Periwinkles as Food 18. CALYPTR^EID.E "Bonnet 

 Limpets "The Grotto-shells, Phorus 19. TURBINID.E Trochus 20. HALIOTID.E The Ear-shell, Haliotis Uses 

 of Pearly Shells Pleurotomaria Its Rarity 21. IANTHINHXE lanthina, "Floating Shells" The Raft 22. 

 Fi.ssuRELLlD.iE 23. NERITID.E 24. PATELLID.E "Limpets" Used as Food How the Oyster-catcher Detaches 

 them 25. DENTALlAD.fi 26. CHITONID^: Multivalve Snails Order II.. PULMONIFERA Air-breathers 

 Anatomy of a Snail Inoperculata, or Land Snails without Operculum Characters Curious Experience of a Desert 

 Snail 27. HELICID.E Used as Food The Largest Land Shell Known The Odontophore, or Tooth-bearing Tongue 

 Other Genera 28. LIMACID.E The Slugs The Mucus Secretion and its Uses 29. ONCIDIAD.E 30. LIMN^EID.E Air- 

 breathing Pond Snails 31. Af RICULID.E -Operculata, or Operculated Land Snails 32. CYCLOSTOMID.E 33. HELICINIDA: 

 34. ACICULID.E Order III., OPHISTHOBRANCHIATA 35. TORNATELLID.E 36. BULLION 37. APLYSIAD^: 

 "Sea Hares" 38. PLEUROBRANCHID.E 39. PHYLLIDID.E The "Sea Slugs" 40. DORID^E 41. TRITONIAD.E 42. 

 JSOLID.E 43. PHYLLIRHOID.E 44. ELYSIAD.E Order IV., NUCLEOBRANCHIAT A Oceanic Snails 45. FIROLID.E 

 The Carinaria 46. ATLANTin. Class III., PTEROPODA Their Pelagic Character Their Abundance Source 

 of Food to the Right Whale Their Wing-feet compared to Moths Delicacy of their Shells Distribution. 



Division b. HOLOSTOMATA.* In the section already described, the SIPHOXOSTOMATA are marked 

 (as we have seen) by the respiratory siphon protruding from the anterior canal of the shell, 

 indicating their carnivorous propensities. In this section, the HOLOSTOMATA, the respiratory siphon 

 is not (as a rule) so produced, and the mouth of the shell is therefore entire, and not drawn out into 

 a canal in front. The animal has usually a short, non-retractile muzzle ; the gills are comb-like or 

 plume-like. Most of this division are vegetable-feeders and dwellers in marine or fresh water. 



FAMILY VIII. NATICIDvE. 



In this family the shell is globular, with few whorls ; its spire is small and obtuse ; the aperture 

 is semi-lunar, with an acute lip ; the pillar of the shell is often thickened by a callus. The animal 

 has a long, retractile proboscis ; the lingual ribbon is linear ; the foot is very large, the mantle-lobes 

 enveloping the greater part of the shell. All the species of this family are marine. 



In the genus Natica the shell is smooth and thick and the inner lip callous ; the umbilicus is 

 large, having a spiral callus. The operculum is sub-spiral and shelly. The animal is blind ; the foot 

 is large, having a fold in front protecting the head ; the lobes of the foot cover part of the shell. The 

 animal is carnivorous, feeding on the smaller bivalves. (Gould.) They are 

 themselves devoured by the Cod and "Haddock and the larger Star-fishes. The 

 eggs of the Natica are agglutinated into broad and short spiral bands, un- 

 attached. The animal frequents sandy and gravelly bottoms, from low 

 water to ninety fathoms. (Forbes.) 



The colour-markings on the shells of Natica are very indestructible ; 

 they are frequently preserved in fossil shells. The species are numerous ; 

 more than ninety have been described distributed from the Arctic Seas, the 

 shores of Britain, and the Mediterranean, to India, China, America, Australia. 

 They occur also in the Caspian. NATICA PAPILIONIS. 



In the genus Sigaretus the shell is ear-shaped, the aperture is very wide 



and oblique, the surface of the shell is striated, the operculum is minute, horny, and sub-spiral. The 

 shells of the flatter forms are entirely concealed by the mantle of the animal ; the convex forms are 

 partially so. The epidermis is yellowish. The foot is enormously developed in front. Twenty-six 

 species are described living in the East and West Indies, China, and Peru. 



In the genus Velutina the animal has a thin shell and a velvety epidermis ; the spire is small, 

 the suture deep, and the aperture very large and rounded ; the shell has no operculum. The margin 

 of the mantle is developed all round, and turned up over the shell ; gills, two ; head broad ; tentacles 

 blunt, far apart, eyes at their outer bases. The animal is carnivorous. Four species are described 

 from Britain, Norway, and North America. 



* From holos, entire ; stoma, mouth. 



