SEMI0N0TID2E. 
59 
Type. Imperfect trunk, wanting head. 
The type species of the so-called Ischypterus, attaining a length 
of about 0*2. Trunk regularly fusiform, the depth of the caudal 
pedicle more than one-third as great as the maximum depth of the 
abdominal region. Length of head with opercular apparatus about 
equal to the maximum depth of the trunk, and somewhat more 
than one-quarter of the total length of the fish. Pelvic fins arising 
nearer to the anal than to the pectorals and immediately in advance 
of the dorsal; anal fin, with seven rays, partly opposed to the 
hinder half of the dorsal. Scales smooth and not serrated, those 
of the middle of the flank scarcely deeper than broad ; dorsal ridge- 
scales acuminate. 
Form. Sf Log. Triassic : Massachusetts, Connecticut, and New 
Jersey, TJ.S.A. 
P. 1036. Imperfect fish; Durham, Connecticut. Egerton Coll. 
P. 1035. Pish with well-preserved squamation; Boonton, New 
Jersey. Egerton Coll. 
P. 3511. Impression of trunk apparently deepened by distortion 
in the abdominal region; Massachusetts. 
Enniskillen Coll. 
P. 1017 a, b. Two small specimens, one wanting head, the other 
wanting caudal region ; Sunderland, Mass. Egerton Coll. 
P. 3511 a. Fragmentary remains, probably of this species ; Sunder- 
land. Enniskillen Coll. 
Semionotus tenuiceps (Agassiz). 
1835-36. 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. New 
York, vol. iv. p. 38, pi. ii. 
1837. Eurynotus tenuiceps, J. H. Redfield, ibid. p. 39. 
1841. Palceoniscus latus, W. C. Redfield, Amer. Journ. Sci. vol. xli. 
p. 25. 
1841. Eurynotus tenuiceps, E. Hitchcock, Geol. Massachusetts, vol. ii. 
p. 459, pi. xxix. figs. 1, 2. 
1850. Ischypterus latus, SirP. Egerton, Quart. Journ. Geol. Soc. vol. vi. 
p. 10. 
1857. Eurinotus ceratocephalus, E. Emmons, Amer. Geology, pt. 6, 
p. 144, pi. i xa. //Z • 
1860. Eurinotus ceratocephalus, E. Emmons, Man. Geology, ed. 2, 
p. 188, fig. 164. 
