FOSSIL FISH. 411 



and the caudal fin especially does not present the very singular 

 character of that genus, in having the lower side longer than 

 the upper. 



ExoccETUs, JExocootus exiliens. This impression may, 

 perhaps, belong to a species of the flying fish ; nevertheless, 

 the pectoral fins are very small, and the head very thick. 

 Probably, after all, it does not differ much from the last. 



MuGiL. M, brevis, De Blain. ; Polynemus quinquinarius, 

 Ichth. Ver. This impression, about six inches long, which 

 was unique at the time in which Volta wrote, has evidently 

 belonged to a spinous fish, with two separated dorsal fins. 

 It very probably approximated to mugil, and consequently to 

 Polynemus ; but nothing is less certain than that it is a species 

 of this last genus. The portions of what M. Volta considers as 

 analogous to the fine kinds of separated rays of the dorsal fin, 

 would seem to be placed under a vertical line through the 

 eyes, whereas, in the quinquinarius ^ they are much further 

 back. The head, moreover, of the fossil is very stout. 



Trigla. Triyla Cyra. An impression is referred by 

 M. Volta to this fish, which is very abundant in the Mediter- 

 ranean, but the impression does not appear sufficiently com- 

 plete to establish this identity ; indeed, the smallness of the 

 pectoral fins, and the total absence of any indication of de- 

 composed rays, would lead us to the belief that it was not a 

 trigla, but rather, perhaps, a true abdominal fish. 



Scomber. Scomber pelamis, Volta. An impression, ten 

 inches long, complete enough to identify it with the genus in 

 question, but not sufficiently so to determine the species. 



iS. altalunga, Volta. The great length of the pectoral 

 fins seems to justify this analogy. 



S. thynnus, A fine impression, twenty-eight inches long, 

 pretty well preserved as to the general form, though the head 

 has no character that can be recognized. There is, however, 

 much of the tunny in the general appearance. This fossil is 



