CLASSIFICATION OF DEVONIAN FISHES. 



21 



Poll/ pter ICS, ^^^^fc, has an elongated body, with a depressed 

 head; and a conically tapering caudal extremity. The orbits are 



Fig. \5. 



Figure of Pohjpterus (after Agassiz). 



situated in the fore part of the head, while the gape extends far 

 back. There are two large principal jugular plates, without lateral 

 or median plates. The pectoral arch is covered inferiorly by two 

 triangular osseous plates, which meet in the middle line, and 

 are superficial to the so-called coracoids. The pectoral and 

 ventral fins are lobate. The caudal fin is rliomboidal and nearly 

 diphycercal.* 



A comparison of these characters with those which have been 

 assigned to Glyptolmmus, or to Osteolepis, reveals at once the close 

 connexion of the three genera, f from which however Polypterus 

 diff(3rs in many important particulars. 



Thus the parietal bones of Polypterus are much smaller, in pro- 

 portion to the frontals, than are those of either Osteolepis or 

 Glyptolcemus, and with age they unite with one another and with 



* See the careful account of the tail of Polypterus, by Kolliker, " Ueber das Ende der 

 Wirbelsiiule der Ganoiden." 



t I do not know that any one has hitherto pointed out in detail the very close relation 

 between Pohjpterus and the fossil genera enumerated above ; but Professor Pander has 

 enunciated conclusions nearly similar to my own in the following passage (Ctenodip- 

 terinen, p. 3.) : — 



" Ueberhaupt ist es merkwurdig zu sehen wie Polypterus so ganz in den Hintergrund 

 " gestellt wird, Herr J. Miiller (Ueber d. Bau.) sagt ausdriicklich ' Fur den Polyptei us 

 " ' kenne ich unter alien fossilen Ganoiden keine analogic.' Und Herr Pictet wieder- 

 " holt dasselbe gleichfalls, ' aucun fossile n'a etc rapproche de ce genre remarquable.' 

 " Wir werden in Zukunft sehen dass wenn man iiberhaupt ein Recht hat, wie es doch 

 " wahrscheinlich ist, die ausgestorbenen Geschlechter der Devonischen Formation jetzt 

 " noch lebenden Fischen an die Seite zii stellen, mehrere durch ihre Zahnbau, durch die 

 " grossen Knochen-platten und die Stelle der Kiemenhaut-strahlen, durch den Bau der 

 " Kopfknochen, u.s.w., eine grossere analogie mit dem Polypterus als seinen Amerika- 



uischen Zeitgenossen besitzen." 



In his subsequent memoirs Prof. Pander has not followed out to their logical result the 

 views so sagaciously indicated in this paragraph, which I think would be identical with 

 those I had arrived at before I read it, and now publish. 



