RESTORATIONS OF THE HEAD OF OSTEOLEPIS. 181 



Restorations of the Head of Osteolepis. By Edwin S. Goodrich, F.R.S., 

 Zool. Sec. L.S., Fellow of Merfcon College, Oxford. 



(With 6 Text-figures.) 



[Read 17th January, 1918.] 



The genus Osteolepis is one of the commonest and best-known of the early- 

 Devonian Teleostomes. Nevertheless the exact disposition and homology of 

 the superficial bones of the head are still but imperfectly understood. Two 

 recently published restorations of the head, one by Gregory (6) and the other 

 by Watson and Day (14), differ so remarkably from each other that it seemed 

 advisable to reinvestigate the subject ; for the Osteolepidpe are a very 

 interesting and important group. In many respects, as for instance in the 

 form of the paired fins and in the cosmoid structure of the scales, they 

 approach the Devonian Dipnoi such as Dipterus (Goodrich, 4, 5) ; while, on 

 the other hand, the skull shows undoubted affinity with the e;irly Amphibia 

 (Stegocephali). Huxley, I think unfortunately, in his valuable work on the 

 fishes of the Devonian epoch (7), included Osteolepis and its fossil relatives 

 together with Polypterus in the one group Crossopterygii. Polypterus, 

 however, as I have endeavoured to show elsewhere (5), really differs funda- 

 mentally in its structure from the Osteolepids, and is almost certainly an 

 aberrant Actinopterygian preserving some primitive characters. But, how- 

 ever this ma}' be, there can be little doubt that the Osteolepidse have departed 

 less from the structure of the common ancestor of the Teleostomi and 

 Tetrapoda than any other known fish. A thorough understanding of the 

 structure of the skull of Osteolepis is, therefore, of the greatest importance for 

 the elucidation of the homologies of the bones in the higher Vertebrates. 



The most complete restorations of the skull of Osteolepis yet published 

 are those given by Pander in his well-known monograph (10). But, 

 beautiful as are his figures and excellent his reconstructions, they r can by no 

 means be trusted in every detail. Since then, Traquair has contributed a 

 very good restoration of the whole fish (13), without detailed figures of the 

 head ; and Smith Woodward in his text-book (15) has given a figure of the 

 roof of the skull, which is in all essentials correct. As already mentioned 

 above, in his interesting discussion of the origin of the Tetrapoda (6) 

 W. K. Gregory has figured restorations of Osteolepis microlepidotus, admit- 

 tedly based on Pander's work ; while D. M. S. Watson and H. Day, in their 

 valuable paper on "Palfeozoic Pishes" (14), restore Osteolepis maerolepidotus. 

 Three sets of these figures from Pander, Gregory, and Watson it Day are 

 here reproduced for comparison (figs. 2, 3, 4, & 5). 



