GASTEROPODA. 299 
fund by Mr. Cunnington, in fields near Devizes), just dis- 
turbed from its sleep; s, the shell; m, the contracted 
mantle. 
Distribution, 8 species. South Europe, Canary Islands, 
Britain (introduced)? 
Fossil, 2 species. Tertiary. 
Famity JIT.—OncIpIADZ. 
Animal, slug-like, destitute of any shell, completely covered 
by a coriaceous ‘mantle; tentacles cylindrical, retractile, with 
eyes at their extremeties ; foot much narrower than the mantle, 
OncrpiuM, Buchanan. 
_Lype, O. Typhee, Buch. 
Litymology, diminutive of onkos, a tubercle. 
Animal oblong, convex, usually tuberculated; head with 2 
retractile tentacles, bearing the eyes; mouth covered by a 
notched yeil; no horny jaws; tongue broad, with above 10 
rows of lingual teeth (in O. celticwm), teeth 54.1.54;* the 
central teeth minute, triangular, with a single obtuse spine; 
laterals shghtly curved; heart opistho-branchiate ; respiratory 
orifice posterior, distinct from the vent; sexes combined, ¢ organ 
under the right tentacle, 9 at the posterior extremity of the 
body. 
Distribution, 16 species. Britain, Mediterranean, Red 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 haye been separated under the name Peronia, Bl. 
(Onchis, Fér). One species (0. celticwm) 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 (oncidioides), Lesson. Named after Dr. F. 
Hamilton (Buchanan), the zoologist of India. 
Animal oval, entirely covered by asimple mantle; respiratory 
orifice in the centre of the back; head with 4 tentacles, retractile 
* This is a convenient mode of stating the number of lin ual teeth in each row; it 
means that there is a single (symmetrical) tooth in the centre, and 54 lateral (uns 
symmetrical) teeth on each side. If the numb r of rows of teeth on the dental mem: 
brane is known, it may be added below this—Peronia Mauritiana, &2.* 82 
