42 INTRODUCTION. 



A Cyrena, the same as or very nearly allied to the 

 Cyrena consobrina, which is common in the Nile, near 

 Alexandria. Mr. G. So werby calls it Cyrena trigonula ; 

 but I do not think it is the species so named by 

 Lamarck. 



And, 



Unio littoralis Lam. (Mag. N. Hist, series 2., 

 548. f. 27.), which is common in the French rivers ; 

 and is also found in the Swedish ones. 



There are also found fossil in the older strata many 

 other species, which are all different from any of the 

 existing ones. The land shells found in these strata 

 are of a much larger size than those now found in 

 Europe, and resemble more nearly the tropical species ; 

 but still, as they are not the exact representatives of 

 exotic species, this is no proof that they were inhabit- 

 ants of that kind of climate. The following species 

 among others, have been described : — 



1. Helix globosa. Sow. M. C. ii. t. 170. 



2. Bulimus ellipticus. Sow. M. C. iv. t. 337. 

 3. castellatus. Sow. M. C. iv. t. 366. 



4. Limnceus longiusculus. Sow. M. C. t. 343. 



5. fusiformis. Sow. M. C. t. 169. f. 23. 



6. minimus. Sow. M. C. t. 169. f. 1. 



7. maximus. Sow. M. C. t. 328. f. 61. 



8. columellaris. Sow. M. C. t. 328. f. 2. 



9. pyramidalis. 



10. Ancylus elegans. Sow. M. C. t. 533. 



11. Planorbis cylindricus. Sow. M. C. t. 140. f. 2. 



12. obtusus. Sow. M. C. t. 140. f. 3. 



13. lens. Sow. M. C. t. 140. f. 4. 



14. euomphalus. Sow. M. C. t. 140. f. 7—9. 



15. Melania fasciata. Sow. M. C. t. 24]. f. 1. 



