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Cincinnati Society of Natural History. 



EXPLANATION OF PLATE VI. 



Pig. i — Right side of left pectoral spine of Heter acanthus uddeni ; 

 natural size. 



Fig. 2. — Anterior side of same; natural size. 



Fig. 3. — Transverse section of shaft at 3A, fig. 2 ; natural size. 



Fig. 4. — Outline of transverse section of same at 4 A, fig. 2; nat- 

 ural size. 



Fig. 5. — Outline of section taken obliquely across the basal portion 

 of the spine at 5A-5A, fig. 1 ; natural size. 



Fig. 6. — Portion of anterior side at 6A, fig. 2; enlarged. 



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