52 



Brit., vol. 2, p. 373, pi. 16, fig. 3. L. Limosa. Flem. 

 Brif. An,, p. 275. L. P. Gray's Turt., p. 233, pi. 9, 

 fig;. 101. Common. 



L. PALUSTRIS. Helix P. Turt. Lin. H. Stagnalis, var. 

 Pen. Brit. Zo., vol. 4, pi. 86. fig. 136. B. H. P. Mont. 

 Test. Brit., vol. 2, p. 370, pi. 16, fig. 10. Flem. Brit. 

 An., p. 274. Gray's Turt, p. 239, pi. 9, fig. 107. Not 

 common. 



* TRUNCATULUS. Helix Fossaria. Mont. Test. Brit., 

 vol. 2, p. 372, pi. 16, fig. 9. L. F. Flem. Brit. An., 

 p. 274. L. T. Gray's Turt., p. 240, pi. 9, fig. 108. 

 Irregularly distributed. Montagu found it " upon the top 

 of one of the highest hills in Cornwall, at the verge of a 

 spring near the Lizard, where no other species of shell 

 was to be found ". 



L. GLABER. Helix Octona. Pen. Brit. Zo., vol. 4, 

 pi. 86, fig. 135. H. Octanfracta. Mont. Test. Brit,, 

 vol. 2, p. 396, pi. "11, fig. 8. L. Octona. Flem. Brit. An., 

 p. 274. L. G. Gray's Turt., p. 242, pi. 9, fig. 106. 

 The indefatigable Montagu says, " we have found it only 

 in one part of England, a splashy place by the road side 

 (a muddy pool by the side of the high road on the top of 

 a hill) half way between Fowey and Looe in Cornwall, 

 where they were plentiful in all stages of growth ; the 

 young are less slender, and have only five or six volutions." 

 Such however have been the changes effected within the 

 space of forty years, that I have hitherto failed in dis- 

 covering these shells. 



PLANORBTS. 



GENERIC CHARACTER : The shell discoidal, spire 



depressed, and all the whorls appearing above and beneath ; 



aperture oblong, lunate, distant from the axis ; cavity 



simple; margin not reflexed. 

 P. MARGINATUS. Helix Complanata. Turt. Lin. H. 



Planorbis. Pen. Brit. Zo., vol. 4, pi. 83, fig. 123. Borlase's 



Nat. Hist, of Corn., pi. 28, fig. 8. H. C. Mont. Test. 



Brit., vol. 2, p. 450. P. C. Flem. Brit. An., p. 278. 



P. M. Gray's Turt., p. 265, pi. 8, fig. 87. Introduced 



on the authority of Borlase. 



NERITACEA. 



The shell, of the river or sea, flattened oval, without 

 Columella; left margin of the aperture resembling a half 

 partition. 



NERITA. 

 GENERIC CHARACTER: Shell semiglobular or oval, 

 flattened below ; and without an umbilicus. Aperture 

 semicircular; the left margin flat, acute; without denta- 



