. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology; Zoology. SASTMAN: CARBONIFEROUS FISHES FROM THE CENTRAL WEST. 215 Stethacanthus productus Newberry. (Text-figure 14.) 1875. Physonemiis gigas {errore) St. John and Worthon, Pal. Illinois, Vol. VI., PI. XVII., Figs. 7-9. 1897. Stethacanthus productus J. S. Newberry, Trans. N. Y. Acad. Sci., Vol. XVI., p. 291, PI. XXIII., Figs. 2,2. 1897. Stethacanthus compressus J. S. Newberry, Ibid., p. 292, PI. XXIIL, Figs. 3, 4. Type. — Imperfect spine; Mu- seum of Chicago University. The spines referred to this species are characte
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology; Zoology. SASTMAN: CARBONIFEROUS FISHES FROM THE CENTRAL WEST. 215 Stethacanthus productus Newberry. (Text-figure 14.) 1875. Physonemiis gigas {errore) St. John and Worthon, Pal. Illinois, Vol. VI., PI. XVII., Figs. 7-9. 1897. Stethacanthus productus J. S. Newberry, Trans. N. Y. Acad. Sci., Vol. XVI., p. 291, PI. XXIII., Figs. 2,2. 1897. Stethacanthus compressus J. S. Newberry, Ibid., p. 292, PI. XXIIL, Figs. 3, 4. Type. — Imperfect spine; Mu- seum of Chicago University. The spines referred to this species are characterized by hav- ing the concave margin very gently curved, in consequence of which the apex is much inclined backwards. The smaller spines described by Newberry as S. com- pressus appear to be the young of the species under discussion, and it need scarcely be remarked that their correlation by this au- thor with the pectoral and pelvic fins is entirely fanciful. Spines having the same form as S. pro- ductus, but of much smaller size, occur in the Kinderhook lime- stone of Iowa. The species de- scribed by Messrs. St. John and Worth en as Physoncmus depressus, P. carinatus, and P. gigas (in part) are distinguished from one another and from S. productus in only minor details, and the types are extremely fragmentary. Nev- ertheless, it is convenient to re- gard the Kinderhook species as distinct from the Burlington, provisionally at least, and as rep- resenting the earliest and most primitive expressions of the ge- nus. The Burlington species ex- hibit a marked increase in size, and in the next succeeding for- mation, the Keokuk, the maximum appears to have been attained by spines such as the one represented in the accompanying Fig. 14. Stethacanthus productus Newb. Keokuk lime- stone, Keokuk, Iowa. Lateral aspect of spine, with cross-sections of summital portion, X ^ (approximately).. Please note that these images are extracted from scanned page images that may have
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