GASTEROPODA. 299 



fC'Und by Mr. Cunnington, in fields near Devizes), ju?t dis- 

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

 mantle. 



Distrihution, 3 species. South Europe, Canary Islands, 

 Britain (introduced). 



Fossil y 2 species. Tertiary. 



Family III. — Oi^"cidiad.e. 



Animal, slug-like, destitute of any shell, completely coyerod 

 by a coriaceous mantle ; tentacles cylindrical^ retractile, with 

 eyes at their extremeties ; foot much narrower than the mantle^ 



Onciditjm, Buchanan. 



Tijpe, 0. Typhce, Buch. 



Etymology, diminutive of onJcos, 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, 5 at the posterior extremity of the 

 body. 



Distrihution, 16 species. Britain, Mediterranean, Eed 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 Peronia, 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.) 



? Buchanania [oncidioicles), Lesson. Named 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 number of lin ual teetli in each row ; it 

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

 symmetrical) teetli on each side. If the numb r of rows of teetli on the dental mero 

 brane is known, it may be added below tin ^—Peronia Mauritiana, -8-2-.^ 2-2- 



