teeth. The posterior of this specimen (not figured) has the lateral tooth 

 parallel with the hinge strongly developed. No. 39, Whitehorse collection. 



8c. — Right valve of a specimen, showing only two radiating ridges. No. 

 38, Whitehorse collection. 



8d. — Squeeze from mold of right valve of specimen, with beak and hinge 

 line missing, showing five ridges. 



Be.— The mold of the above specimen, showing lamellar striae in the 

 sinus below the umbo and the impressions of the "granulations" below the 

 beak. No. 58, Dozier collection. 



Pleurophorus albequus longus. Page 162. 



9.— Cast of right valve. Front and posterior end broken away. No. 40, 

 Whitehorse collection. 



Spirorbis sp. Page 148. 



10. —View of cast of attached surface shown on cast of a shell. Greatly 

 magnified. No. 44, Whitehorse collection. 



Aviculopecten oklahomaensis. 



11. —A somewhat broken specimen of a left valve, about natural size. 

 No. 21, Whitehorse collection. 



11a.— Another individual, probably compressed antero-posteriorly, making 

 the beak appear narrower and sharper than it should. There is also a slight 

 difference in the size of the ribs and the concentric markings are not brought 

 out so strongly as they should be in the drawing. No. 16, Whitehorse col- 

 lection. 



116.— Mold of a small specimen; lie is a rough squeeze of the same en- 

 larged, showing the undulating striae sometimes found upon specimens of 

 this species. No. 15, Whitehorse collection. 



