150 



dilated, compressed and very oblique; rather concave above, to receive the 

 ligament, which is partly internal, and partly external. 



S. australis, S. Mediterranea. 



Amphidesma. Shell transverse, inequilateral, subovate or rounded, some- 

 times gaping a little at the sides; hinge having one or two teeth, and a narrow 

 pit for the internal ligament. Ligament double; one external, short; the 

 other internal, fixed in the cardinal pits. 



A. variegata, 

 ' donacilla, 

 ' lactea, 

 ' cornea, 



A. albella, 

 ' lucinalis, 

 ' Boysii, 

 ' tenuis, 



variegatum, 



pulchrum, (Sowerby, C. 111. f. 2. 

 pallidum, ' 3. 



formosum, ' 8. 



roseum, ' 1. 



ellipticum, < Z. P. f. 17. 



australe, ' 4. 



corrugatum, ' 18. 



subtruncatum, ' 19, 20. 



solidum, (Gray, Sp. Z. Part I. pi. vi. f. 6. 

 cordiforme, (Chemnitz, xi. 1941, 1942. 

 rupium, (Sowerby, C. 111. f. 10. 

 cancellatum, (Sowerby, Sp. C. f. 8. 



A. flexuosa, 

 ' prismatica, 

 ' phaseolina, 

 ' corbuloides, 



A. glabrella, 

 ' purpurascens, 

 ' nucleola, 

 ' physoides. 



A. lamellosum, (Sowerby, Sp. C. f. 



' rcticulatum, 



' crenulatum, 



' duplicatum, 



' punctatum, 



' purpurascens, 



' multicostatum, 



' lenticulare, 



' teve, 



' prismaticum, 



' tenue, 



' Boysii, 



' Siculum, 



C. 111. f. 



Sp. C. f. 

 C. 111. f. 



Sp. C. f. 



9, 10. 

 11, 12. 

 13. 

 14, 15. 



7. 



5. 

 16. 



9. 



6. 

 21. 

 22. 

 23. 

 24. 



CORBULEA.— Two Genera. 



Shell inequivalve, ligament interior. 



Corbula. Shell regular, inequivalve, inequilateral, closed or very slightly 

 gaping. One large conical, curved, ascending tooth in each valve, with a 

 pit beside it; no lateral teeth. Ligament internal, inserted in the pits. 



C. australis, 

 ' sulcata, 

 ' erythrodon, 



C. ovalina, 

 ' Taitensis, 

 ' nucleus, 



C. impressa, 

 ' porcina, 



C. semen, 



4 fossil species. 



Pandora. Shell regular, inequivalve, inequilateral, transversely oblong, 

 upper valve flat, and the lower convex. Two oblong, diverging, unequal, 

 cardinal teeth in the upper valve; two oblong pits in the other. Ligament 

 internal. 



P. rostrata, 



P. obtusa. 



