AET. 20 A NEW ALASKAN GENUS OF MOLLUSKS KIRK 9 



Plate 2 

 Pycnodesma benjamini, new species 



Fig. 1. View of right side of the type specimen. Cat. No. 71276, U.S.N.M. 



2. Anterior view of same specimen. 



Pycnodesma giganteum, new species 



3. Interior of left valve showing posterior portion of hinge plate. 



4. Interior of right valve of another specimen showing anterior portion 



of hinge plate, teeth, and small muscle scar. Cat. No. 71275 

 U.S.N.M. 



Pycnodesma giganteum, new species? 



5. Interior of right valve of same specimen figured as PI. 1, fig. 6, 



showing striated wall of ligamental fossa, teeth, and large muscle 

 sear. Cat. No. 71277, U.S.N.M. 



Mcgalodon (Eumegaiodon) cucullatus (Goldfuss) 



6. Interior view of left valve. 



Middle Devonian, Paffrath, near Cologne, Germany. Cat. No. 

 15527, U.S.N.M. 



Megalomus canadensis Hall 



7. Interior view of right valve. 



Guelph (middle Silurian), Elora, Ontario. Cat. No. 71278, U.S.N.M. 

 All figures approximately X 2/3. 



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