mSULARCM MADERENSIUII 149 



Species ita dieta, quòd ad fluentium aciunrum didcium lipas gaiidet. 

 Primiis in Madera clariss. Rev.'' Loweus inveiiit. 



Gen. Planorbis, Múller 



Testa dextrosa, orbiculato-depressa s. discoidea, multispiralis: spira saojie 

 depressissima; aiifractus pluiimi, uliiiique conspicui, supra axiii fcie liorisuuta- 

 lem convoluti: aperliira simplex, obkiiigo-lunaris, elliplica v. suliqiindiala, ah 

 axe remotissima, latior quàm alta; pèristoma ténue, acutiini, incoiripIcUim, su- 

 periore margine inferiorem ultra protenso. — Animal haud timidum, capite ro- 

 busto, probostidiformi, tentaculis '2 setaceis. flliíbrmibus, ociílis ad basin exb'a 

 sitis, pede ovato, brevi, lingua denlibus pliirimis, quadialis, uncinalis, seriatim 

 transverse armata. — Cum Limnaois comniixium, gregarium, in orbis mediis re- 

 gionibus borealibusque, raro in australibus, aquáticas edens plantas in fluminibus 

 rivuiisque. 



Plauorbis glalter, JelTreys 



Testa umbilicata, médio depressa, ecarinata, tenuis, olivaceo-fusca, inter- 

 dum viridescens, transverse sublililer striatula, nitidiuscula; spira vaide de- 

 pressa, ápice concava; sutura profunda; umbilicus magnus; anfi-actus 4-5 con- 

 vexiusculi s. subterete,s, celeriter accrescentes, aiiquando anguiati, ultimus \k 

 tongitudinis vix superans, turgidus, antice non descendens; apertura obliqua, 

 ovato-iotundata, aljja; perisloma simplex, snbacutuni, continuum, externo mar- 

 gine reflexiusculo, interno columellae adnato. — -Animal tardam, timidum, cor- 

 pore fusco-lutescente, ca|)ite fusco, tentaculis pallidis, brevibus, cylindiicis, ápice 

 obtusis, pede amplo, marginibus luteulis. 



Alt. l, lat. 4 mill. 



Planoibis gtaber, JetTr. Trans. Linn. Soe. 

 » lacvis Gray Man. 



Haliifal fiequens in Europa ad rivulos fontesque lignis lapidibusque immer- 

 sis gregaiio adliaei-ens; in Maderae convallibus haud rara, cum A.-íliiviatili Mull. 

 et T.-lruncatula Drap. promiscue degens. 



Obs. líx Lusitânia, ubi ad rivulos fontesque frequens, in Maderam insulam 

 forsan translala. 



Genus sic nominalum ob testam orbicularem compressamque s. plana- 

 tam. 



Species ita dieta, qnòd testa glaberrima. 



Primus in Madera invenit clariss. Jolmsonus. 



