CLASSIFICATION OF DEVONIAN FISHES. 



11 



me to separate naturally allied genera, and, still more, because the 

 ''dendrodont" character is quite as strongly marked in other fishes, 

 e.g., Megalichthys, whicli certainly do not belong to the same family 

 as Gyroptychius, though undoubtedly related to it. 



The resemblances which obtain between Gyroj)tycJiius, on the 

 one hand, and Osteolepis, Diplopterus, &c. on the other, have been, 

 well pointed out by Professor Pander, whose Monograph upon the 

 Saurodipterini is not less excellent than that already cited, though 

 it should not be forgotten that Hugh Miller long ago published 

 an excellent restoration of Osteolepis.^' Diplopterus has, in fact, 

 the elongated form, depressed head, forward orbits, long gape, 

 and conically tapering candal end of the body, which characterize 

 Glyptolwmus. The pectoral fins are similarly, though not so acutely, 

 lobate, and the lobate ventrals are situated far back, as in the 

 last-named genus. The second dorsal is over the anal, and the 

 caudal fin is rhomboidal and diphycercal. 



On the other hand, Osteolepis, though similar to Diplopterus in 

 many essential respects, has a very ineequilobed tail, much like that of 

 Glyptolepis. But in Osteolep is^ as in its most nearly allied genera, the 

 cranial bones and the scales are quite smooth. The three occipital 

 plates of the skull remain distinct, but the other bones of the roof 

 of the' cranium have coalesced, so as to form two bucklers, an 

 anterior and a posterior ; in which, however, the outlines of the 

 primitive cranial bones, which have, on tlie whole, an arrangement 

 similar to that which obtains in Glyptolcem.us, are traceable. There 



Fig. 8. 



Restoration of Osteolepis (after Pander). 



* See " The Old Red Sandstone," PI. iv. fig. 1, Osteolepis major. It appears from this 

 figure that even the lobation of the pectoral fin had not escaped Hngh Miller, though he 

 does not particularly refer t© it in the text. Before Professor Pander's work appeared in 

 this country, I had obtained from Caithness, by the well-directed activity of Mr. Peach, 

 and placed in the Museum of Practical Geology, a series of specimens illustrating all the 

 chief structural characters of Osteolepis as detailed above. The lobate pectorals of 

 Osteolepis and Diplopterus are exhibited very well by specimens in the Ilunterian and 

 British Museum ; the fact that " small ganoid scales are continued upon " the bases of the 

 pectorals being noted in the description of No. 567 in the Catalogue of the former 

 Museum. 



