PLATE XVIII 



PELECYPODA: EUFAMEFPIBRANCHIA 



A. OsTRACEA 



r. Lima cardiiformis, Sby, Fossil : Oolite. 



2. Lima subauriculata, Mont. 



3. Ostvea Ricovdcana, d' Orb. Fossil: Chalk. 



4. Pinna nohilis, Finn. The anterior adductor (a.) comes into line 

 with the posterior adductor {a'.) in the main axis of the animal, and die 

 hinge is aborted ; p. is the scar of the pedal retractor muscle. 



Another example of the Ostracea is shown on Plate XXX., Fig. 5. 



B. SUBMYTILACEA 



5. Dreissensia polymorpha, Pallas. This species, originally an in- 

 habitant of the British Isles, became extinct, and. was re-introduced 

 about 1824 on timber from the Baltic, and is now widely distributed s 

 even penetrating water-mains. 



6. Astarte sulcata, Da C. 



7. Crassatella pulchra, Reeve. 



8. Cardita calyculata, Finn. 



9. Cyprina Islandica, Finn. 



10. Isocardia humana, Finn. 



11. Lucina Pennsylvanica. Finn. 



12. Galeomma Turtoni, Sby. 



13. Montacuta substriata, Mont. 



14. Lepton squamosum, Mont. 



15. Corbicula consobrina, Caill. 



16. SphcEYium conieum, Finn. 



17. Unio littoralis, Cuv. 



Other Submytilacea are shown on Plate XV., Figs. 3, 5, 6, and 9; 

 Plate XVI. , Fig. 3 b ; Plate XXX., Fig. 9; Plate XXXIF, Figs. 14 

 and 18. 



C. Tellinacea 



18. Tellina lingua-fclis, Finn. 



19. Donax denticulatus, Finn. 



20. Mactra stultorum, Finn. 



%* All Figs, from drawings by S. P. Woodward. 



