86 ANNUAL REPORT OF 



berry to be about six inches, the extreme of eight inches being 

 only rarely attained. 



Semionotus tenuiceps (Agassiz). 



183S-36. Eurynotus tenuiceps, L. Agassiz, Poiss. Foss., vol. ii., pt. i., pp. 159, 



303, pi. xiv. c, Figs. 4, 5. 

 1837. Palceoniscus latus, J. H. Redfield, Ann. Lyceum Nat. Hist., N. Y., vol. 



iv., p. 38, pi. ii. 

 1837. Eurynotus tenuiceps, J. H. Redfield, ibid., p. 39. 



Eurynotus tenuiceps, E. Hitchcock, Geol. Mass., vol. ii., p. 459, pi. xxix., 



Figs. 1, 2. 

 Palceoniscus latus, W. C. Redfield, Amer. Journ. Sci., vol. xli., p. 25. 

 Ischypterus latus, Sir P. Egerton, Quart. Journ. Geol. Soc, vol. vi., p. 10. 

 Eurinotus ceratocephalus, E. Emmons, Amer. Geology, pt. 6, p. 144, 



pi. ix a. 

 Eurinotus ceratocephalus, E. Emmons, Manual Geologjr, ed. 2, p. 188, 



Fig. 164. 

 Ischypterus latus, R. H. Traquair, Quart. Journ. Geol. Soc, vol. xxxiii., 



P- 559- 

 Ischypterus tenuiceps, J. S. Newberry, Monogr. U. S. Geol. Surv., vol. 



xiv., p. 32, pi. v., Figs. 1-3; pi. vii., Fig. 3. 

 Ischypterus latus, J. S. Newberry, ibid., p. 46, pi. liii., Fig. 3. 

 Allolepidotus americanus, W. Deecke, Palaeontogr., vol. xxxv., p. 114. 

 Semionotus tenuiceps, A. S. Woodward, Cat. Foss. Fishes Brit. Mus., 



pt. iii., p. 59. 

 Semionotus tenuiceps, W. H. Hobbs, 21st Rept. U. S. Geol. Surv., pt. 



iii., p. 56 (11011 pi. 4). 

 Semionotus tenuiceps, G. F. Eaton, Amer. Journ. Sci. [4], vol. xv., 



P- 295. 



1841 



1841 

 1850, 



1857 



i860 

 1877 



1888 

 1889 



1895 



1901 

 1903 



A species attaining a total length of about 20 cm., and readily 

 distinguished from all others (except in young stages) by the 

 excessive development of the dorsal ridge-scales ; these are very 

 large and conspicuous, and, in mature individuals, comparatively 

 obtuse. The anterior dorsal outline is considerably arched, 

 usually forming a characteristic "hump" immediately behind the 

 head. Length of head and opercular apparatus less than the 

 maximum depth of the trunk, and contained four times in the 

 total length of the fish. Fins as in S. fultus. Scales smooth 

 and serrated, those of the middle of the flank in part twice as 

 deep as broad. The dorsal ridge-scale immediately in advance 

 of the dorsal fin has its posterior border obtuse, and not pro- 

 duced, and the corresponding ridge-scale in front of the anal fin 



