CATALOG OF FOSSIL FISHES IN THE CARNEGIE MUSEUM Byal 
servées. Aussi en rapportant 4 ce genre l’empreinte fossile que je vais décrire, je 
me suis laissé guider uniquement par la forme générale du poisson.” 
Further on, in his description of the holotype of 7’. tenuiceps, the same author 
observes: “Quoique on ne voit pas la dentition de l’intérior de la guele, la forme 
générale du poisson, les proportions du corps, et cet air de famille si inappréciable en 
histoire naturelle, compensent ce qu’il y a de défectueux dans les détails, et comme 
on ne peut balancer qu’entre les genres Platax et Trachinotus, il ne peut rester aucun 
doute sur sa position générique dans la famille des Secomberoides.”’ 
The above paragraphs are of interest as revealing the mental process, or personal 
equation on the part of an experienced student of ichthyology, who depended upon 
instinct, as it were—that is, an acquired second sight or delicacy of perception, or ina 
word feeling—in determining the systematic position of doubtful or of imperfectly 
preserved fossil remains. Be that as it may, no one has shown cause for removing 
Agassiz’s so-called Trachynotus tenuiceps from the position assigned to it, and until 
the present time the type specimen has remained absolutely unique. 
The Carnegie Museum is fortunate in possessing two well preserved examples 
which may be provisionally referred to the species described by Agassiz, although 
they greatly exceed the type in size, and one, which has a deeper form of body than 
Agassiz’s original, may be found on further investigation to differ from it suffi- 
ciently to warrant the establishment of a separate species. The doubtful specimen 
last mentioned is illustrated in Plate C. 
25. Trachynotus tenuiceps Agassiz. (Plate XCI, fig. 1.) 
1796. Chetodon rhomboides (errore) G. S. Volta, Ittiolit. Veronese, p. 162, pl. 
XXXIX, fig. 3. 
1835. Trachinotus tenuiceps L. Agassiz, Poiss. Foss., Vol. V, pt. I, p. 36, pl. VII. 
Type.—Nearly perfect fish in counterpart; Paris Museum of Natural -History. 
Of the two examples provisionally referred to this species, the larger (Cat. No. 
4367) is preserved on a single slab, the other in counterpart (Cat. No. 4532, 4532a). 
One of the containing slabs of the latter is shown in the accompanying plate. The 
individual which is not figured has a total length to base of the caudal fin of 16 cm. 
Genus ZANCLUS. 
Of this existing genus two fossil species have been described, one from the 
Eocene of Monte Bolca, the other from the Calcaire Grossier of Paris. No examples 
of either are found to be in the British Museum, and the undermentioned specimen 
of Z. brevirostris is the only one thus far reported besides the type. A figure of the 
recent Z. cornutus is given by Agassiz, Poiss. Foss., Vol. IV, pl. G, fig. 1. 
