ANODON. 275 



sloping upwards, and forming an angle with the fore 

 part of the shell. In M. cygneus the base slopes 

 upwards; and M. incrassatus diiFers from them all 

 by its large exserted ligament, superior roughness of 

 the outside, and in having the posterior part, in a 

 slope from the umbones to the base, incrassated. 

 {Linn, Trans, xiii. 87.) 



The Abbe Dupuy divides the French species into 

 sections, thus : — 



a. Cygncai. — Shell very large, thin, with the mus- 

 cular scars scars slightly marked. 



1. A. cygnaea. 



/S. Ponderosa. — Shell large, very thick, especially 

 in front, muscular scars deep. 



2. A. ponderosa, Dupuy, t. 1. f. 12. — 3. A. 



Dupuy i, t. 17. f. 13. — 4. A. subponderosa, 

 t. 17. f. 14. — 5. A. Rossmassleriana, t. 18. 

 f. 14. 



7. Anatina. — Shell small, generally shorter and 



thinner than the preceding, with the muscular 



scars less deep. 



6. A. anatina, t. 19. f. 13, 14.; t. 20. f. 20. — 



7. A. piscinalis, t. 19. f. 17, 18. — 8. A. 



scaladiana, t. 19. f. 12. — 9. A. Rayii, t. 20. 



f. 22. — 10. A. coartata, t. 20. f. 21. — 11. 



A. Milletii, t. 21. f 16. 



h. Hiantes — Shell middle size or small ; valves 

 more gaping on the lower front edge than the 

 preceding. 

 12. A. Gratelupeana, t. 17. f. 22. 



T 2 



