SEMIONOTIDiE. 
55 
Genus SEMIONOTUS, Agassiz. 
[Neues Jahrb. 1832, p. 144.] 
Syn. Ischypterus, Sir P. Egerton, Quart. Journ. Geol. Soc. vol. iii. 
1847, p. 277. 
Trunk fusiform. Marginal teeth slender, conical, and somewhat 
spaced, inner teeth stouter; opercular apparatus well-developed, 
with a narrow arched preoperculum. Ribs ossified. Fin-fulcra 
large. Paired fins small; dorsal fin large, arising at or behind the 
middle of the back and in part opposed to the relatively small anal; 
caudal fin slightly forked. Scales smooth or feebly ornamented, 
and the narrow overlapped margin not produced at the angles ; 
flank-scales not more than twice as deep as broad, and those of the 
ventral aspect nearly as deep as broad ; the dorsal ridge-series of 
acuminate scales forming a prominent crest. 
Semionotus bergeri, Agassiz. 
[Plate II. fig. 3.] 
1832. Palceoniscum arenaceum , H. A. C. Berger, Yerstein. Sandst* 
Coburg. Gegend. p. 18, pi. i. fig. 1. 
1833. Semionotus spixi, L. Agassiz, Poiss. Foss. vol. ii. pt. i. p. 8 (name 
only). 
1833-36. Semionotus bergeri, L. Agassiz, ibid. pp. 8, 224, pi. xxvi. 
figs. 2, 3. 
1834. Semionotus bergeri , L. Agassiz, Neues Jahrb. p. 380. 
1843. Semionotus esox, H. A. C. Berger, Neues Jahrb. p. 86. [Dis¬ 
torted fish; Royal Geological Museum, Gottingen.] 
1851. Semionotus bergeri , C. von Scliauroth, Zeitschr. deutsch. geol. 
Ges. vol. iii. p. 405, pi. xvii. 
1854. Semionotus, J. G. Bornemann, ibid. vol. vi. p. 612, pi. xxv. 
1854. Semionotus bergeri, H. A. C. Berger, Neues Jahrb. p. 321. 
(P) 1861. Semionotus bergeri, 0. Fraas, Wurth Jaliresh. vol. xvii. pp. 93, 
94, pi. i. fig. 6. 
1864. Semionotus bergeri, J. Striiver, Zeitschr. deutsch. geol. Ges. 
vol. xvi. p. 305, pi. xiii. figs. 1, 3, 4. 
Type. Imperfect fish ; University Geological Museum, Gottingen. 
The type species, a fish more than three times as long as its 
greatest depth, attaining a length of about 0*18. Trunk regularly 
fusiform, the depth of the caudal pedicle somewhat more than one- 
third as great as the maximum depth of the abdominal region. 
Head with opercular apparatus occupying nearly one-quarter of 
the total length ; the external bones sparsely tuberculated. Pelvic 
fins arising nearly midway between the pectorals and the anal; 
dorsal fin arising immediately behind the middle of the back, much 
