118 CLASS III. GASTEROPODA. ORDER VII. PECTINIBRANCHIATA. 
The Ancyli, which may be said to partake of the characters of the 
Lymnee and the Chiline, are for the most part found in clear running 
streams, upon the leaves of different species of water-plants. 
Examples. 
Pl. CXCIII. Fig. 1. 
AnoyLus FLuviaTIcis, Miller, Verm., p.201. Draparnaud, Hist. Moll. 
Fluv. et Terr., pl. 2. f.23 and 24. Turton, Manual, p. 140. f. 125. 
Patella fluviatilis, Gmelin 
Patella cornea, Poiret. 
Pl. CXCIII. Fig. 2. 
AncyLus Lacustris, Miller, Verm., p. 199. Draparnaud, Hist. Moll. 
Fluv. et Terr., pl. 2. f. 25,27. Turton, Manual, p. 141. f. 126. 
Patella lacustris, Linnzeus. 
Patella oblonga, Dillwyn. 
Order VII. GASTEROPODA PECTINIBRANCHIATA. 
Branchiz pectinate, in cavitate dorsali supra collum impositz ; cavitate 
siphone aut appendice siphonali propter aque fluxum interdum in- 
structa. Animal aut phytiphagum, aut zoophagum, operculo ple- 
rumque instructum. 
This order contains by far the largest portion of the Gasteropoda, and 
it is moreover that portion most especially esteemed by conchologists. 
The animals referred to it are all water-breathing mollusks, distinguished 
by the pectinated structure of their branchie, which are for the most part 
arranged in parallel lamellz, like the teeth of a comb, and contained 
within a dorsal cavity above the neck. This cavity, necessarily requiring 
to be constantly supplied with the surrounding fluid, is sometimes fur- 
nished with a fleshy siphon of various length, for the influx and reflux of 
the water ; sometimes, however, it merely takes the form of a short si- 
