PLATE XXVI. 



CoNCHiDiUM DECDSSATUM (page 293). 



Figure 1. Dorsal view of a fine specimen of this species, from the Silurian lime- 



stone at the Grand Hapids of the Saskatchewan, shewing the whole 

 of the dorsal valve, and the prominent umbo and recurved beak of the 

 ventral. 



Figure 2. Outline of the posterior end of a oast of the interior of both valves of an- 



other specimen of this species, shewing the relative convexity of the 

 two valves, the length and other characters of the mesial septum of the 

 ventral valve, and the nature of the two short septa in the dorsal. 

 Both figures of this species are from drawings by Mr. L. M. Lambe. 



Glassia variabilis (page 273). 



Figure 3. Ventral view of a typical specimen of this species, from the Silurian lime- 



stone at the Winisk River. 



Figure 4. Dorsal view of another typical specimen, from the same locality. 



Figure 5. A specimen from the Winisk Biver, that has been broken in such a way as 



to shew a transverse section of the closed valves at about their mid- 

 Iqngth, with the direction of the spiralia. All three figures three 

 times the natural size. 



Glassia variabilis (?) Var. (page 252). 



Figure 6. Ventral view of a specimen from the Ekwan River, which may represent a 



local variety of this species, with a deeper sinus in the ventral valve. 

 Figure 6 a. Front view of the same specimen. 



II 6 5. Dorsal view of the same. All three figures three times the natural size. 



Glassia variabilis (page 277). 



Figure 7. Dorsal view of a specimen from the Silurian rocks of the Fawn River. 



Figure 8. Similar view of another specimen from the same rocks. 



Figure 9. Similar view of a third specimen from these rocks. 



