Pi AE, Sexe 
STETHACANTHUS TUMIDUS, Newb. (p. 198). 
Fig. 1. Spine, natural size. 
Berea grit, Berea, Ohio. 
2. Spine with fin attached, side view, half natural size, slightly restored from impression in shale 
over grit. 
Berea, Ohio. 
24, Spine No. 2 seen from above, half natural size. 
CTENACANTHUS Lirront, Newb. (p. 201). 
3. Spine, base and part of ornamented surface, natural size. 
Saint Louis limestone, Saint Louis, Mo. 
ASTEROPTYCHIUS ELEGANS, Newb. (p. 176). 
4. Spine, natural size. 
Waverly sandstone, Grindstone City, Mich. 
HOPLONCHUS PARVULUS, Newb. (p. 170). 
5. Spine, natural size. 
Cleveland shale, Bedford, Ohio. 
ACONDYLACANTHUS OCCIDENTALIS, N. & W., sp. (p. 206). 
6. Spine, natural size. 
Saint Louis limestone, Alton, IL. 
280 
