PLATE I. 



Unless otherwise stated, all the figures are of natural size. 



Unio Albertensis (page 3). 



Figure 1. Side view of the type specimen, sliewing the left valve. 



Anomia perstrigosa (page 4). 



Figure '1. Upper valve of a perfect and well preserved specimen, as 

 viewed frona above. 



CORBICULA OCCIIIENTAMS (pagO 7). 



Figure 3. Side view of a large specimen from Hyo-<-irass flat, sliewing the 

 right valve. 

 " 3((. The same as seen from aboxe- 



CoRBECULA OBLIQUA ( pagO 8). 



Figure 4. Side view of a perfect specimen, from Ryc-<-irass Hat. 

 " 4". Dorsal aspect of the same. 



" ill. Cast of a left valve, witli a sliglitly diiierent outline, from the 

 Belly liivor. 



CoRBULA PER.VNliLTLATA (pagoMj. 



Figure 5. Side view of a somewhat arcuate examijle, from Uye-'irass Hat. 



" .5«. Dorsal view of the same, to show the amount of convexity 



of the closed valves and the excavated posterior area. 



')b. Side view of a younger specimen from the same locality. At 



this stage of growtli the posterior area is not excavated and 



the posterior extremity is truncated. 



