GASTEROPODA. 303 
slender, the eyes at their inner bases; lingual teeth sub- 
quadrate, central and marginal bicuspid, laterals tricuspid ; 
excretory orifices on left side of the neck. 
Some species of Planorbis have the suturesandspire deeply sunk, 
and the umbilicus flattened ; specimens occur with 
the spire elevated (Fig. 130*). P contortus, a minute 
species, has above 6,000 teeth. (Cocken.) P. corneus 
secretes a purple fluid. (Lister.) P. lacustris (Seg- 
mentina, Fleming) has the whorls contracted inter- 
nally by periodic septa, 3 in a whorl, with triradiate 
openings. P. armigenus (Planorbula, Haldeman) Fig. 189. 
has 5 teeth in the aperture which nearly close the passage. 
Distribution, 145 species. North America, Europe, India, 
-China. 
Fossil, 69 species. Wealden—. Britain, France. 
Gundlachia, ancyliformis, Pfeiffer, 1850. Fresh waters. Cuba. 
Shell thin, obliquely conic; apex inclined posteriorly; base 
closed for two-thirds by a flat, horizontal plate; aperture semi- 
circular. 
FAMILY V.—AURICULIDA. 
Shell spiral, covered with horny epidermis, spire short, body- 
whorl large ; aperture elongated, denticulated ; internal septum 
progressively absorbed. 
Animal with a broad and short muzzle, tentacles, 2, cylin- 
drical, the eyes sessile behind them ; mantle-margin thickened ; 
orifices as in the snails; foot oblong; sexes united; mouth 
with a horny upper jaw; lingual teeth numerous, central series 
distinct, hooked, tricuspid. A. livida has about 31 laterals 
(Loyén); another species examined by Mr. Wilton has 11 
large laterals and about 100 smaller (wncini) on each side, 
gradually diminishing towards the edge (Fig. 131): c, central 
teeth; 7, laterals. 
AAGTITITG 
POTN 
my Vy Ia NCU tin AN 
Wy ) 1 , AP] f PO 
AA it MINT 
AOA SSS 
WY NN 
i PD) x ms ; Nuwurtn anna ugNaRRTARNATANEAN 
wu if Cc 2 6 ae 
Pr 
Fig. 131. 
The <Awricule frequent salt-marshes, damp hollows, and 
places overflowed by the sea; they were long regarded as 
marine animals, and their shells confused with those of 
Tornatella and Ringicula. 
* P. margmatus, var. Rochdale, communicated by J. S. Gaskoin, Esq. 
