140 



DESCRIPTION OF THE PLATES. 



f'O, PAGE 



Plate X. 



1,2,3. Ancylus fluviatilis 94 



4,5,6. Ancylus lacustris 95 



7, K, 9, 10, 11, 12. Dreissena 



polymorpha 9S 



Plate XI. 



1. var. 1, Anodon Cygneus .... 99 



2, .3. Anodon Cygneus, young. 99 



Plate XII. 



1. var 2, Anodon cellensis 100 



2. Anodon cellensis, young .... 100 



3. var. 6, Anodon complanata. 102 



4. Anodon complanata, young . 102 



Plate XIII. 



1. var. 3, Anodon Anatina 101 



Plate XIV. 



1. var. 4, Anodon stagnalis ... 102 



Plate XV. 



1, var. 8, Anodon ponderosa... 104 



2, 3. Anodon ponderosa, var. . 104 



Plate XVI. 



1, 2. var. 11, Anodon I'ostrata. 105 



3, 4. var. 9, Anodon subrhoni- 



bea 104 



Plate XVII. 



1, 2. var. 5, Anodon intermedia 102 



3. var. 10, Anodon piscinalis... 105 



4, 5. Anodon piscinalis, young. 105 



Plate XVIII. 



1, 2. var. 12, Anodon contorta 106 



3. var. 7, Anodon Avonensis... 103 



4,5. Unio ovalis Ill 



6,7. Unio Batavus Ill 



8. Unio Batavus, young Ill 



Plate XIX. 



1. Unio pictorum, ordinary form 107 



''JG- PA6U 



2. Unio pictorum 108 



3. Unio pictorum 108 



4. Unio pictorum, ordinary form 108 



Plate XX. 



1,2. Unio rostrata 109 



3,4. Unio Deshaysii 108 



Plate XXI. 



1. Internal view of teeth of 

 Unio rostrata 109 



2. External view of teeth of 

 Unio rostrata 109 



3. Internal view of teeth of 

 Unio Deshaysii 108 



4. External view of teeth of 



Unio Deshaysii 108 



5. Internal view of teeth of 

 Unio tumidus 110 



6. External view of teeth of 

 Unio tumidus 110 



7. External view of teeth of 



Unio pictorum, ordinary 



form 107 



8,9. Unio tumidus 110 



10. Internal view of teeth of 

 Unio Batavus Ill 



11. External view of teeth of 

 Unio Batavus Ill 



12. External view of teeth of 

 Alasmodon Roissyi 114 



13. External view of teeth of 

 Alasmodon margaritiferus. 112 



14. External view of teeth of 



Unio ovalis Ill 



Plate XXII. 



1. var. 1, Alasmodon marga- 



ritiferus 112 



2, 3. var 2, Alasmodon Roissyi 114 



Plate XXIII. 



1. var. 5, Alasmodon olivacea . 115 



2. var. 3, Alasmodon minor ... US 



3. var. 4, Alasmodon arcuata.. 115 



