CLASSIFICATION OF DEVONIAN FISHES. 



3 



The pectoral arcli is covered by two triangular, sculptured, osseous 

 plates (Pet ^ Pct^), "which meet in the middle line below and are 

 superficial to the so-called coracoids. The paired, or pectoral and 

 ventral, fins are lobate ; that is, the fin has a central axis, or stem, 

 covered with scales. There are two dorsal fins, placed in the pos- 

 terior half of the body. The ventral fins are situated under the first 

 dorsal, and are succeeded by a single anal. The caudal fin, whose 

 • contour is rhomboidal, is divided into two equal lobes by the pro- 



longed conical termination of the body ; in other words, the fish is 

 diphycercal, or truly homocercal.* 



Every ichthyologist will admit the singularity of this combination 

 of characters, but a careful analysis of the structural peculiarities 

 presented by other fossil fishes of the same age, will show, that, so 

 far from isolating Glyptolwmiis, they closely unite it with several 

 other genera. 



That genus which appears to me to approach it most closely is 

 the Gyvoptychius of M'Coy, whose structure has received admirable 

 elucidation from Professor Pander in his beautiful monograph 

 Ueber die Saurodipterinen, Dendrodonten, Glyptolepiden und 

 Cheirolepiden des Devonischen Systems" (1860), to which I may 

 refer those who desire to obtain a more particular accjuaintance 

 with the details of its organization. 



Here I must content myself with reproducing in a reduced wood- 

 cut (fig. 8) Professor Pander's restoration of the fish, which may 



Fig. 3. 



Restoration of Gyroptycliius (after Pander). 



be compared with the restored woodcut of Glyptolcemus (fig. 1), 

 and with the Plates, and with stating that the head, the body, and 

 the fins of Gyroptycliiv^s might be described in the terms which have 

 just been applied to Glyptolcemus. Pander, hov/ever^ makes no 



* I have endeavoured to show elsewhere (Quarterly Journal of Microscopical Science, 

 Oct. 1858) that the so-called "homocercal " Teleostei of the present epoch are in reality 

 excessively heterocercal ; but the word " homocercal " is now so generally understood 

 to signify a tail like that of most existing Teleostei, that I prefer to employ I'rof. M'Coy's 

 term " diphycercal " for truly homocercal tails. See, on this point, Kdlliker, " Ueber das 

 Ende der Wirbelsiiule der Ganoiden, 1860," and Van Beneden, " Sur le Developpement 

 de la Queue desPoissons Plagiostomes," Bull, de I'Acad. Royale Belgique, 1861. 



