PLATE XIJ. 



Figure 1. Leperditia Selvnjnii, sp. nov, a, left valve; b, ventral edge. 



" 2. The same, a, left valve; b, edge view ; c, end view. 



** 3. The same, a, right valve ; b, ventral edge ; end view. 



" 4. The same. Ventral edge, partly exposed, of a left valve. 



'' 5. The same. Interior of the united ventral edges. Figs. 1-5 from Anti- 

 costi. Magn. 2 diam. 



" 6. Portion of slab with casts and moulds of Leperditix from the Grand 

 Rapidfi, Saskatchewan River. Magn 2 diam. 



" 7. Leperditia cvcca, nov. Magn. 4 diam. Grand Rapids. 



" 8. Hisingeri, Schmidt, var. egena, nov. a, right valve ; b, ven- 

 tral edge ; c. end view. Magn- 4 diam. Grand Rapids. 



" 9. cscca, nov. Left valve. Magn. 2 diatn. Below Cedar Lake. 



" 10. exigua. Left valve. Magn. 25 diam. Island on east side of 



Lake Winnipegosis. 



" 11. Whiteavem, noN . Right valve. 



" 12. a, left valve ; b, ventral edge ; c, end view. Figs. 11 



and 12. Magn. 2 diam. Chemahawin, Saskatchewan 

 River. 



" 13. — a, left valve retaining its shell, but broken behind 



and damaged at the centre; b, ventral aspect; c, end 

 view. Magn. 2 diams. From Old Fort Island, Cedar 

 Lalce. 



" 14. Left valve. Magn. 2 diam. Chemahawin. 



" 15. Hisingeri, Schmidt, ysly. fabulina, nov. a, right valve; b, 



ventral edge ; c, end view. Magn. 3 diam. Foot of the 

 Grand Rapids, Saskatchewan River. 



