GLOCHIDIA OF FRESHWATER MUSSELS. 9 



aaa. Depth greater than length. 



Symphynota complanata, 0.310 by 0.320 mm. (fig. 6). 

 Symphynota costata, 0.385 by 0.390 mm. (fig. 7). 

 Alasmidonta truncata, 0.3.50 by 0.380 mm. (fig. 42). 

 Proptera type: 



Glochidium varying greatly in size in the different species; axe-head shape; with 

 two spines, one at each of the ventral corners of the shell, or spineless. 



1. Glochidium with spines. 



a. Size large. 



Lampsilis alata, 0.220 by 0.380 mm. (fig. 8). 

 aa. Size rather small. 



Lampsilis capax, 0.105 by 0.185 mm. (fig. 9). 



2. Glochidium without spines (?). 



aaa. Size small. 



Lampsilis Ixvissima, 0.100 by 0.155 mm. (fig. 10). 

 Lampsilis type: 



Glochidium semicircular, or semi-elliptical; ventral margin rounded; no spines 

 present. 



1. Glochidium semi-elliptical; ventral margin rounded. 



a. Hinge line short and evenly curved, or undulate. 

 b. Size large. 



Plagiola securis, 0.230 by 0.330 mm. (fig. 14). 

 Lampsilis iris, 0.240 by 0.300 mm. (fig. 46.) 

 Lampsilis luteola, 0.250 by 0.290 mm. (fig. 15). 

 Lampsilw subrostrata, 0.270 by 0.330 mm. (fig. 16). 

 Lampsilis recta, 0.220 by 0.280 mm. (fig. 17). 

 Lampsilis ligamentina, 0.220 by 0.260 mm. (fig. 18). 

 Obavaria retusa, 0.240 by 0.295 mm. (fig. 47.) 

 Quadrula granifera, 0.290 by 0.355 mm. (fig. 19). 

 Quadrula pustulosa, 0.230 by 0.290 mm. (fig. 20). 

 bb. Size medium. 



Lampsilis anodontoides, 0.185 by 0.210 mm. (fig. 21). 

 Lampsilis fallaciosa, 0.200 by 0.240 mm. (fig. 22). 

 Lampsilis higginsi, 0.210 by 0.260 mm. (fig. 23). 

 Lampsilis trabalis, 0.193 by 0.255 mm. (fig. 40). 

 Lampsilis ventricosa, 0.205 by 0.255 mm. (fig. 24). 

 Obovaria ellipsis, 0.210 by 0.265 mm. (fig. 25). 

 Quadrula metanevra, 0.175 by 0.200 mm. (fig. 26). 

 Quadrula pustulata, 0.200 by 0.250 mm. (fig. 27). 

 bbb. Size very small. 



Lampsilis gracilis, 0.070 by 0.095 mm. (fig. 28). 

 Plagiola donaeiformis, 0.060 by 0.063 mm. (fig. 29). 

 Plagiola elegans, 0.060 by 0.070 mm. (fig. 30). 

 aa. Hinge line straight, or slightly depressed. 

 c. Size small. 



Tritogonia tuberculata, 0.085 by 0.100 mm. (fig. 31). 

 la. Ventral margin obliquely rounded. 

 aaa. Hinge line long. 

 d. Size large. 



QuMdrula heros, 0.260 by 0.340 mm. (fig. 32). 



