The Cambridge natural history . )ly to fresh-water operculate Ciasterop(xla. But the passao-efrom a marine to an aerial life involves much profomider changes<if environment, wliich have to be met l)y correspondinglv im-portant changes in the organism. This may be in part tlif, ^ SB. K. Akad. ITiss. IVicn, 1889, p. 4, but the view i« not Fig. 10. —Trigonia ^jec-(inata Laru., Sjduey,\ i6 ORIGIN OF FRESH-WATER UNIVALVES reason why the ancestry of <ill Iuhuonata, whether land or fresh-water, is so (lifficnlt to tract. (h) Gasteropoda. — (I) Oprrculatc. Caniducnnd
The Cambridge natural history . )ly to fresh-water operculate Ciasterop(xla. But the passao-efrom a marine to an aerial life involves much profomider changes<if environment, wliich have to be met l)y correspondinglv im-portant changes in the organism. This may be in part tlif, ^ SB. K. Akad. ITiss. IVicn, 1889, p. 4, but the view i« not Fig. 10. —Trigonia ^jec-(inata Laru., Sjduey,\ i6 ORIGIN OF FRESH-WATER UNIVALVES reason why the ancestry of <ill Iuhuonata, whether land or fresh-water, is so (lifficnlt to tract. (h) Gasteropoda. — (I) Oprrculatc. Caniducnnd C/ea areclosely allied, with but little nioditication, tothe marine Cominellu^ (i^g- H)^ ^^ i^ <l^*JSfassodonta to JVassa. They occur (in freshwater) in the rivers of India, Indo-China, Java,and Borneo, associated with essentially fresh-water species. Potamides, witli its varioussubgenera {Tel esc opium, l^yrazvs, Pirenella,^amarine^eiius,which Gerithidea,),A\\ ofwhich inhabit swamps andlives between tide mudflats just above high-water mark in all warm marks, and from i • i\- n -±1 ? i o\ which is proLahiy Countries, are derived iromCertt/num (1ig. 12):derived B, Clea, ^i Assim iHca, Jli/drohia, ixiid -^erha^s Tru7icateU<i,from Itissoa. It is a remarkable fact that in
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
