GASTEROPODA. 79 



species. Ordinary limpets (Patdlidce) of unequivocal form are 

 found in the Bath oolite, but are afterwards less plentiful, and 

 almost disappear from the tertiaries ; M. d'Orbigny regarded 

 them as generically distinct, but employed for them a name 

 (Hcleion, Mont.) synonymous with Patella. 



Pulmonifera, — The existence of air-breathing snails in the 

 palaeozoic rocks is shown by a small "chrysalis-shell, with a 

 round, not toothed, aperture, CDendropupaS, discovered by Dr. 

 Dawson and Sir C. Lyell in a hollow coal tree of Nova Scotia." 

 Upwards of 40 species of Pupa have been found fossil in eocene 

 strata. The Purbeck limestone contains a modern-looking 

 Pkysa ; and other species of extraordinary size are found in 

 the older tertiary of France, and also in Central India, where 

 the genus does not exist at the present day. The fresh-water 

 eocene of the Isle of Wight and Paris has afforded many spe- 

 cies of Limnoea and Planorbis ; a Glandina rivalling in size 

 the G. truncata of South Carolina ; a Cyclostoma, with a sculp- 

 tured operculum like the Cyclotus Jamaicensis ; and an elon- 

 gated species of the section Megalomastoma, which is now liv- 

 ing in both East and West Indies. At Hordle has been found 

 the little Helix labyrinthicus, still living in Texas ; and in the 

 smith of France occur representatives of the Brazilian genera 

 Megaspira and Anastoma (fig. 19, 9). In the mioecne is found 

 another genus (Ferussina, fig. 19, 10) resembling the lamp-snail, 

 but supposed to be operculated. The Pulmonifera of the Eng- 

 lish pliocene are in a few instances extinct, at least in England ; 

 nearly all are still living here, but more or less abundant now 

 than they were in the times of the mastodon and elephant. 

 The extinct land-snails of the Atlantic islands Madeira and 

 Porto Santo are associated with remains of many recent species 

 occurring in numbers which have relatively altered, telling the 

 same tale of gradual changes, affecting some species prejudici- 

 ally, but favourable to the increase of others. The fossil land- 

 snails of St. Helena were supposed by Mr. Darwin tohavebecome 



