10 



GLOCHIDIA OF FRESHWATER MUSSELS. 



2. Glochidium semicircular. 



a. Hinge line long and nearly straight. 

 h. Size medium. 



Quadrula ebena, 0.160 by 0.150 mm. (fig. 33). 



Quadrula plicata, 0.200 by 0.200 mm. (fig. 34). 



Quadrula solida, 0.160 by 0.160 mm. (fig. 35). 



Quadrula trigona, 0.160 by 0.155 mm. (fig. 36). 



Trundlla sulcata, 0.200 by 0.205 mm. (fig. 37). 



Unio gibbosus, 0.200 by 0.215 mm. (fig. 38). 

 aa. Hinge line shorter, with gradual curve. 



Obliquaria reflexa, 0.225 by 0.235 mm. (fig. 39). 



3. Glochidium semicircular. 



a. Ventral margin obliquely rounded. 



b. Hinge line long, straight or slightly curved, 

 c. Size medium. 



Cyprogenia irrorata, 0.210 by 0.185 mm. (fig. 11). 

 Pleurobema sesopus, 0.220 by 0.200 mm. (fig. 12). 



4. Glochidium kidney-shaped. 



a. Hinge line long and straight, or nearly so. 

 b. Size medium. 



Drovms dronius, 0.190 by 0.100 mm. (fig. 13). 



ILLUSTRATIONS. 



1. Alasmidonta calceola. 



2. Anodonta imbecillis. 



3. Strophitus edentulus. 



4. Anodonta corpulenta. 



5. Arcidens confragosus. 



6. Symphynota complanata. 



7. Symphynota costata. 



8. Lampsilisalata. 



9. Lampsilis capax. 



10. Lampsilis Isevissima. 



11. Cyprogenia irrorata. 



12. Pleurobema sesopus. 



13. Dromus dromus. 



14. Plagiola securis. 



15. Lampsilis luteola. 



16. Lampsilis subrostrata. 



17. Lampsilis recta. 



18. Lampsilis ligamentina. 



19. Quadrula granifera. 



20. Quadrula pustulosa. 



21. Lampsilis anodontoides. 



22. Lampsilis fallaciosa. 



23. Lampsilis higginsi. 



24. Lampsilis ventricosa. 



25. Obovaria ellipsis. 



26. Quadrula metanevra. 



27. Quadrula pustulata. 



28. Lampsilis gracilis. 



29. Plagiola donaciformis. 



30. Plagiola elegans. 



31. Tritogonia tuberculata. 



32. Quadrula heros. 



33. Quadrula ebena. 



34. Quadrula plicata. 



35. Quadrula solida. 



36. Quadrula trigona. 



37. Truncilla sulcata. 



38. Unio gibbosus. 



PLATE III. 



39. Obliquaria reflexa. 



40. Lampsilis trabalis. 



41. Encysted young of Plagiola donaciformis, 



showing great growth ot adult shell beyond 

 the margin of the glochidial shell. 



42. Alasmidonta truncata. 



43. Anodontoides ferusaccianus subcylindraceus. 



44. Symphynota compressa. 



45. Anodonta grandis. 



46. Lampsilis iris. 



47. Obovaria retusa. 



