38 Fossil Fishes 



middling size. Head rather small, presenting a finely granu- 

 lated surface resembling shagreen. Bach but slightly arched. 

 Pectoral fins middling. Ventral small, inserted midway be- 

 tween pectoral and anal. Anal large. Dorsal middling, situ- 

 ated opposite the posterior part of the anal. Tail forked, equi- 

 lobed.* Scales extending a little upon the base of the upper 

 lobe. All the fins have a series of ray lets inserted obliquely 

 upon the first or anterior ray, producing a serrated or denticu- 

 late appearance. In this species these raylets are very fine 

 and close, presenting a strong contrast with those of the Pa- 

 leeoniscus J'uUus, where they are so long and stout as to render 

 the term serrate inapt. The succeeding rays have an articulate 

 appearance, and are finely subdivided toward their extremities. 

 The following list of the number of rays in each fin may serve 

 to give an idea of their relative size : 



Pectoral, large and strong, 10 to 12. 



Ventral, - - - about 8. 



Dorsal, ----- 10 to 12. 



Anal, - - - - - 20 to 30. 



Caudal, - - - - - 30 to 40. 

 A remarkably perfect specimen of this species, from the same 

 locality, is now in possession of the Yajc Natural History So- 

 ciety, at New Haven, and is represented in Plate I.t 



In the arrangement of Agassiz, the fish described above would 

 be comprehended in the order Ganoidcs, and family Lejri- 

 doides. Its equilobcd tail would assign it to the second di- 

 vision of the family, the Homocerci, as he lias termed them. 

 From seven fusiform genera now arranged in this division it is 



* This indeed is not strictly the case. Its structure, however, is analogous to 

 thai of the Semionotus, ranked hy Agassiz among the Homocerci, and differs most 

 decidedly from that of the line lliinrocerci, where the scales, and probably the 

 vertebras, extend to the extreme point of the upper lobe. 



t Among the specimens deposited with that society is a species of Palcconis- 

 cus, which differs not only from the /'. Julius, but from the other numerous species 

 of this genus, in its form and proportions, and which I have ventured to name, 

 from this peculiarity, P. talus. Sec Plate II, 



