AESTIVATION OF TROPICAL MOLLUSCA. 509 



various parts where numerous Physas, Succineas, and 

 Water-beetles were observed. In the wilderness at the 

 back of the villa, fine oaks formed natural summer-houses, 

 and groups of large trees, natives of the Mauritius, were 

 mingled with the Gourd and Coffee-tree. In the holes 

 of tree trunks, and under the decayed mass of leaves 

 which strewed the ground, we found numbers of a large 

 Achatina in a state of hibernation. The large Achatina 

 of the Mauritius, during aestivation, forms a strong, 

 dense white epiphragma during the dry season, and con- 

 ceals itself either in holes of decayed trees or under the 

 surface of the soil ; the Megalomastoma of Mindoro 

 closes its shell with its round horny operculum, and con- 

 gregates in numbers in fissures of trees some distance 

 from the ground; the Cerithium truncatmn, in Singapore 

 and Borneo, suspends itself by glutinous threads to dead 

 sticks on the margins of rivers ; the Caracotta of the 

 Philippines, hides under loose bark, where it adheres very 

 closely; the Cydostomata and Scarabi bury themselves 

 under the stratum of dead leaves with which the ground 

 is always covered; the Assiminete, Melanin, and Ampul- 

 larice, conceal themselves in the soft mud of ponds and 

 rivers ; the Nematura adheres firmly to floating sticks, and 

 to the under surface of leaves in stagnant pools ; the 

 snails glue themselves together, as they do in England, 

 and congregate in holes of rotten trunks; the Bulimi 

 adhere firmly to smooth branches and boles of trees; and 

 the Hdicina to the under surface of leaves generally in 

 an elevated situation. The Potomis and Telcscopium 

 bury themselves in the muddy Mangrove swamps, many 

 NcritincB do the same thing, and I have noticed in the 



