FAMILY LYMN.EACEA. 147 



10. Planorbis fontanus. Fountain Planorbis. 



Shell ; depressed, bright amber horny, upper disk with the spire a 

 little immersed towards the apex, lower disk with 

 a moderate-sized sunk umbilicus ; whorls three <^> 



and a half to four, convexly sloping on both sides 

 towards the periphery, which is angularly rather 

 produced ; aperture horizontally triangularly 

 lunar. 



Helix fontanel, Lightfoot (1786), Phil. Trans. Roy. Soc. vol. 



lxxvi. p. 165. pi. ii. f. 1. ' §p 



Planorbis complanatus, Draparnaud (1805), Hist. Moll. 

 p. 47. pi. ii. f. 20 to 22 (not of Studer nor Poiret). 



Helix lenticularis, Alten (1812), Si/st. Abhandl. Augsb. p. 35. pi. ii. f. 4. 



Planorbis fontanus, Fleming (1814), Edin. Eneyc. vol. vii. p. 69. 



Planorbis lenticularis, Sturm (1829), Deutscli. Faun. vol. viii. f. 16. 



Planorbis nitidus, Gray (1840), Turt. Man. p. 268. pi. viii. f. 93 (altered in 

 edit, of 1857 to P. fontanus). 



Hippeutis lenticularis, Hartmann (1842), Erd. und Suss. Qasterop. p. 51. 



Planorbis (Hippeutis) fontanus, Moquin-Tandon (1855), Hist. Moll. vol. ii. 

 p. 426. pi. xxx. f. 10 to 17. 



Hab. Throughout Europe. Siberia. (In ponds and clear streams, on 

 water-plants.) 



Forbes and Hanley and Mr. Jeffreys hare named this species 

 Planorbis nitidus on the ground that it is in chief part the P. niti- 

 dus of Miiller, but Moquin-Tandon has clearly shown that our 

 next species is Midler's P. nitidus ; and he has been followed in 

 that opinion by Dr. Gray. P. fontanus, the smallest of the genus, 

 has a bright transparent amber horny shell of only three and a half 

 to four whorls, sloping in a peculiar quoit-like form towards the 

 periphery, and the aperture assumes a horizontal, triangularly lunar 

 shape. The umbilicus is small compared with its ordinary dimen- 

 sions in Planorbis, and instead of being superficial it has a sunken 

 aspect. The animal is of a dusky grey, sometimes tinged with 

 yellow and finely dark-speckled, timid and slow in its movements. 

 The tentacles are long and filifor*rn, and but little flexuous. The 

 eyes are rather large, round, and black. The species is very 

 generally and widely diffused over the same range of latitude 

 as the preceding. 



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