Bull. U. S. B. F., 1921-22. 



qjl <£> 



*»> ffe 



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Fig. 73. — Juveniles of 20 species of mussels found in the artificial ponds at the U. S. Fisheries 

 Biological Station within two years from the time of construction of the ponds. All reproduced 

 natural size excepting the two right-hand figures in top row which are reduced one-hall. (Photo- 

 graphed by J. B. Southall.) Reading from left to right these mussels are: 



Top row: Anodonta imbecillis, Anodonta corpulent a, Anodonta suborbiculata, Arcidens confragosus. 



Second row: Strophitus edentulus, Symphynota com plan ata. Lampsilis alata, Lampsilis laevisshna. 



Third row: Lampsilis caPax. Lampsilis gracilis, Lampsilis veniricosa, Lampsilis luteola. 



Fourth row: Lampsilis subrostrata. Lampsilis parva, Lampsilis ligamentina, Obovaria -Ihpsis, 



Fifth row: Plagiola donaciformis, Obliquaria refiexa, Quadrula plicata, (Juadrula undata. 



