82 TRIASSIC FISHES AND PLANTS. 
large scales of posterior dorsal line eight, elliptical before, elongate and 
spiny behind, running into fulera of upper margin of dorsal, which are ten 
in number, eight beyond scaled extremity of body, all slender and rod- 
like; caudal fin narrow and weak, oblique, upper lobe longest, rays fifteen, 
slender; fulcra of lower margin fifteen; anal fin narrow, just reaching base 
of caudal, rays eight, fulera ten. 
The most striking diagnostic characters of this species are its pointed 
rostrate, depressed muzzle; conical narrow head, horizontal below; the wedge- 
shaped outline of the body, which is widest near the head; the small and 
delicate fins, and the narrow and oblique tail. The largest specimen which 
I have is ten and a half inches long by three and a half inches wide, the 
smallest five and a half by one and a half inches; but I have seen one speci- 
men which shows distinctly all the characters of the species, and yet is 
only about three and a half inches long. 
This is the most common species of Ischypterus at Durham, Conn., but 
I have not certainly identified it elsewhere. S. W. Loper has good speci- 
mens in his cabinet, and has supplied a fine series of different ages to the 
cabinets of Yale and Columbia. 
The figures given on Pl. IV represent old and half-grown individ- 
uals; that on Pl. XII, Fig. 2, is still younger. 
IscHYPTERUS TENUICEPS Ag., sp. 
Pi. V, Figs. 1, 2,3; Pl. VII, Fig. 3. 
Eurynotus tenuiceps Ag., Poiss. Foss. vol. 2, p. 159, Pl. 14c, Figs. 4, 5; E. Hitchcock, 
Geol. Mass., vol. 2, p. 459; Pl. 29, Figs.1, 2. 
This species has been more fully illustrated than any other from the. 
American Trias. Two figures of it are given by Agassiz in his Poissons 
Fossiles (loc. cit.); two are given by Professor Hitchcock in his quarto Re- 
port on the Geology of Massachusetts; one in Emmons’s Geological Report 
of the Midland Counties of North Carolina, Pl. IX (reproduced in his 
American Geology, pt. 6), a wood-cut probably of this species in Em- 
mons’s Manual of Geology, page 188, andin American Geology, pt. 6, page 
144; also, three figures of it are given on Pl. [Xa of the latter work. Of 
these last cited figures only one has the normal form of the species, the 
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