10 () 
MONSTROSITIES. 
pollution of the water was lellected in the Limitud staijiuilis fonml 
there, which exhibited somewhat swollen transverse growths near 
the mature aperture and the growth lines 
were altogether ruder and stronger in 
character than in ordinary shells. The 
^ following year, when the pollution of the 
f ! water by this chemical refuse was stopi)ed, 
‘ the succeeding generation of shells (puckly 
indicated and reflected the greater purity 
of the water by a reversion to the 
regular outline and smooth even suri'ace 
of mnanal shells. 
Species usually inhabiting tran([uil or 
gently ilowing waters tend to become de- 
formed and dwarfed if subjected to the 
inlluence of strong currents; this is strikingly exemidified in Uuio 
finnidas found in the river Foss, near 
York ; the si)ecimcns found close by 
the overllow or bye-wash of the 
Yearsley Locks, within the inlluence 
of the current, being greatly dwarfed 
and malformeil in their growth, differ- 
ing very markedly from the sym- 
metrically formed and fairly-sized 
shells fre(inenting the sluggishly flowing river a short distance away; 
'Ui h agitated waters are also usually correlated with an increase in 
Kig. — L. sta^i^naiis (I..). 
Lake, I )rink\valcr l*ark, near 
I’rcsiwicli, Lancaslure, 
Collected by Mr. W. fl. Heath- 
cote, K.L.S., 
Showinjx by irregular growth 
tlie baneLil innueucc of the 
chemical refuse formerly cli^- 
charged into the lake. 
Fk.. 227. — L^nio iu/Kidus Phil., 
Yearsley T.ock, near York, 
Cullecled by Rev. \V. C. Hey, M.A., 
Showing the dwarfing and distortion of 
the siieil owing to proximity to the dam. 
Kig. 228 . — Cnio iiouidus Phil., 
Near \'car>Iey Lock, River Ko.ss, ^'ork, collected by Rev. \V. C. Hey, I\L.\., 
.Showing the ordinary form as found a Hiorl di.slance from the dam, in gently Ilowing waters. 
the strength and devehipment of the hinge-teeth or denticles, which 
are liable to become feeble and degenerate in ([uiet and unruflled 
waters. 
