PLATE XVIII 



Kg. 



3. 





3 a. 



Fig. 



4,5. 





4 a. 



PAGE. 



Fig. 1,2. Physonkjiits phoclivus. St. J. and TV 451 



1 a. Side view of small spine; 1 b, view oi' anterior face; 1 c. transverse section near the 



broken tip, posterior face restored ; 1 d, transverse section across the shonlder ; 



1 e. transverse section just above shoulder. Lower fish-bed of the Kinderhook; 

 BurliDgton. Iowa. 



2 a. Side view of a smaller specimen, enlarged two diameters, posterior outline restored ; 



2 &, front view, enlarged two diameters ; 2 c, d, e, transverse sections at points 

 indicated by corresponding letters; rig. 2 b, the posterior face restored in out- 

 line. Same horizon and locality. 



Physoxemus depressus, St. J. and TV 452 



Lateral view of spine, posterior borders restored in outline; 3 b, anterior face; 



3 c, d, e,f, transverse sections. Lower fish-bed Kinderhook ; Burlington, Iowa. 

 Physoxemus carixatus, St. J. and TV" 452 



Side view of fragment showing inferior extremity of spine, restored in outline; 4 6, 

 front view ; 4 c, d, transverse sections. Upper fish-bed Kinderkook j Burlington. 

 Iowa. 



5 a. Side view of a more compressed specimen, restored in outline ; 5 &, c, transverse sec- 



tions. Same horizon and locality. 



Fig. 6-10. Physoxemus gigas, BT. and TV 



6 a. Side view of fragment of large spine, showing tuberculose ornamentation; 6 &, one 



of the anterior tubercles enlarged; 6 e. enlargement of two tubercles of 

 one of the anterior ridges and profile outline; 6 d, similar enlargements of 

 posterior costa-. Upper Burlington limestone ; Louisa county, Iowa. 

 1 a. Side view of imperfect smaller spine, probably referable to above species. Same hori- 

 zon and locality. 



8 a. Lateral view of similar specimen, restored in outline; 8 6, view of anterior face ; 



8 c. d, e,f, transverse sections. Same horizon and locality. 



9 a, b. Side view and transverse section of a very small specimen. Same horizon and 



' locality. 



10 a, b. Transverse sections near the broken tip and base of the original specimen described 



by Messrs. Newberry and TVorthen, Vol. IV, PI. H, fig. 1. Same horizon, 

 Quincy, Illinois. 

 Fig. 11,12 Physoxemus parvulus, St. J. and TV 453 



11 a. Lateral view, restored in outline along the posterior face. Keokuk limestone ; Boon- 



ville, Missouri. 



12 a. Side view and transverse section of a fragment of spine, restored in outline. Same 



horizon, Warsaw, Illinois. 



