452 



others: the whole flicll is fliglitly wrinkled acrofs the 

 whirls : aperture narrow, oval, angulaled. Diameter 

 rather more than half an inch. 



This and the preceding fpecies have been generally 

 confounded together in cabinets under the title of Pin- 

 norbis: but they are perre611y dlftinft, though it is dif- 

 ficult to affix to them their proper fynonyms. There is 

 little doubt, however, that this is the H. Planorbis of 

 Gmelin, and of Muller, as in the chara6}eri(lic de- 

 fcription of the laft author, he fays " carina marginali 

 media," and calls the (liell Planorbis carinatus : and in 

 his Planorbis umbilicata (which we confider as the com- 

 planata of Linn^us) he fays, "carina marginali in- 

 fera;" which well defines the complanata, or what has 

 been termed by BritiJJi conchologifls Helix Planorbis, 

 from a fuppofition it was that (liell of Linn.t;us. 



In order, therefore, to prevent confufion, we have not 

 given the Linncean title to this fpecies, as the name of 

 Planorb's is fo well known to EngliJJi collcftors for a 

 very different fhell ; but have adopted the name given 

 by Muller. 



The great diflinftion of thefe two fliclls i>, that this is 

 not fo thick as the complanata, the body whirl is not fo 

 rounded, but flopes gradually to the carinated ridge, 

 vrhich is not placed fo low, and is equally confpicuous 

 above and beneath; a circumflance not obfervable in the 

 ether. The bafe, or under fide^ in this is more flat, and 



feme- 



