LIMN^ADiE. 271 



7. Segmentina Flem. (Segment Shell.) 



Animal nearly like Planorbis, but the shell is polished, 

 and the cavity contracted by permanent internal 

 transverse ridges, having a triradiated opening. 



So called from the internal segments or par- 

 titions. 



Mr. Alder does not think that the septa in the 

 shell are sufficient to raise it to the rank of a ge- 

 nus, as the animal is exactly like Planoj-bis. Miiller 

 confounded it as a variety with P. fontanus : like 

 that species, the spire is umbilicated, and the front 

 of the shell has the appearance of being the proper 

 spire. 



110.1. Segmentina lineata. Glossy Segment Shell. 



(t. 8. f. 91.) 

 Planorbis nitidus. Miiller, ii. 163. (part) ; Drap. 



p. 46. t. 2. f. 17—19.; Turton, Man. ed. 1. 116. 



f. 91.; Pfidffer, i. 82. t. 4. f. 12, 13. ; Bossm. Icon. ii. 



15. t. 7. f. 114, 115. 

 Hemithalamus lacustris. Leach, Mollusc, p. 137. 

 Nautilus lacustris. Light. Phil. Trans, t. xxvi. 



t. 1. f. 1—7.; Mont. p. 191. t. 6. f. 3. 

 Helix lineata. Walker, Test. M. R. t. 1. f. 28. 

 Planorbis clausulatus. Ferussac ; Potiez §• Mi- 



chaud, Gall. i. 209.; Desmoulin, Mol. Girond. 



n. 10. 

 Segmentina nitida. Flem. Edin. Fncy. xii. 

 Helix nitida. Gmel. 3642. 

 Planorbis nautileus. Kickx, Mol. Brab. 66. 

 Segmentina lineata. Flem. Mollusca, Fncy. Brit. 



t. 367. f. 8., Brit. Anim. 279. 



n 4 



