PLATE LXIII. 



PAGE 



Fig. 1. ABCHIMEDES COMMUNIS ulr 573 



1. Specimen of the axis, showing the remarkable uniformity of the volu- 

 tions. Natural size. 



1 a, 1 b, 1 c. Three fragments of the natural size showing slight variations. 

 1 d. Two sections, natural size, one of a sinistrally, the other of a dextrally 

 wound example showing the inner portion of fenestrated expansion. 

 Chester group, Sloan's Valley, Ky. 

 E. 0. Ulrich's collection. 



'Fig. 2. ABCHIMEDES COMPACTUS Ulr 572 



2, 2 a, 2 6, 2 d. Four specimens of the sub-fusiform axis of this species, 



natural size, showing slight variations. The last is the youngest 



example seen. 



2 and 2 a, Sloan's Valley, Ky. 



E. O. Ulrich's collection. 



2 & and 2 d, Chester, 111. 



Illinois State Museum. 



2 e. Vertical section of axis, natural size. 



Fig. 2 c. ABCHIMEDES iNTEBMEDins Ulr 574 



Vertical section of a strong axis, natural size, showing the outline and 

 the sudden outward bend of the fenestrated expansion. 

 Chester group, Chester, 111. 



Fig. 3. ABCHIMEDES PBOUTANUS Ulr 576 



3, 3 a, 3 b. Three fragments of the axis of this species, natural size, showing 



slight variations in size and volutions. 



3 c. Vertical section of the strongest axis seen, natural size. 



Chester group, Sloan's Valley, Ky. 

 E. O. Ulrich's collection. 



Fig. 4. ABCHIMEDES MEEXANUB Hall 578 



Three fragments of the axis of this species, showing natural size and 

 extremes in thickness of shaft so far noticed. 

 Chester group, Chester, 111. 

 Illinois State Museum. 



Fig. 5. ABCHIMEDES TEBEBBIFOBMIS Ulr 575 



5, 5 o, 5 6. Three fragments of the axis, natural size, showing variations due 



to age and wearing. 



Sloan's Valley, Ky. 



E. O. Ulrich's collection. 

 5 c. Another fragment of the natural size from Chester, 111. 



Illinois State Museum. 



