GASTESOFODA. 299 



fotind by Mr. Cunnington, in fields near Devizes), just dis- 

 turbed from its sleep; s, the shell; m, the contracted 

 mantle. 



Distribution^ 3 species. South Europe, Canary Islands, 

 Britain (introduced). 



Fossil, 2 species. Tertiary. 



Family III.— Oncidiad^. 



Animal^ slug-like, destitute of any shell, completely coyered 

 by a coriaceous mantle ; tentacles cylindrical, retractile, with 

 eyes at their extremeties ; foot much narrower than the mantle 



Onciditim, Buchanan. 



Type, 0. TyphsB, Buch. 



Etymology, diminutive of onkos, a tubercle. 



Animal oblong, convex, usually tuberculated ; head with 2 

 retractile tentacles, bearing the eyes ; mouth covered by a 

 notched veil; no horny jaws; tongue broad, with above 70 

 rows of lingual teeth (in 0. celticum), teeth 54.1.54;* the 

 central teeth minute, triangular, with a single obtuse spine ; 

 laterals slightly curved ; heart opistho -branchiate ; respiratory 

 orifice posterior, distinct from the vent; sexes combined, ^ organ 

 under the right tentacle, $ at the posterior extremity of the 

 body. 



Bistrihution, 16 species. Britain, Mediterranean, Bed Sea, 

 Mauritius, Australia, Pacific. 



The typical Oncidia live on aquatic plants in the marshes of 

 the warmer parts of the Old World. Those which frequent 

 sea-shores have been separated under the name Feronia, Bl. 

 (Onchis, Fer). One species (0. celticum) is found on the coast 

 of Cornwall, congregated in little groups, about a foot or two 

 from the margin of the sea, where the waves break over them. 

 They ascend and descend, so as to maintain their distance as the 

 tides rise and fall ; but they will not bear long immersion in 

 sea-water. (Couch.) 



? Buclianania {pncidioides). Lesson. Kamed after Dr. !F. 

 Hamilton (Buchanan), the zoologist of India. 



Animal oval, entirely covered by a simple mantle ; respiratory 

 orifice in the centre of the back ; head with 4 tentacles, retractile 



♦ Tliis is a convenient mode of stating the numbef of lin Hal teeth in each row ; it 

 means that there is a single (symmetrical) tooth in the centre, and 54 lateral (im- 

 sjTTmietrical) teeth on each side. If the numb r of rows of teeth on the dental mem- 

 brane is known, it may be added below, thi s — Feronia Mavritiana, -^-^'gf^^ 



