G. R. Wieland—On Marine Turtles. 129 



functional value of the epineurals.of Archelon that there are 

 turtles in which following elimination of a true neural series, 

 an overlying dermogene series like that of Archelon has 

 dropped down into the neural position once more. 



The possibility of such cycles is, however, only hinted at. 

 Taking the evidence at its face value, the important point is 

 that Archelon, without having lost the power to develop an 

 ossicular series, or perhaps in spite of having retained such a 

 series, once had a closed carapace and plastron like that of 

 modern turtles. Moreover, the earlier Niobrara Protostegas 

 include the primitive forms like P. Copei and doubtless P. 

 advena with well-developed neurals, and with far less of osteo- 

 dermal development than in the later Archelon. 



It is thus seen that of the two camps which have attacked 

 the difficult and highly attractive problem of the origin of 

 Dermochelys, those favoring the view of a close relationship to 

 other turtles and a comparatively recent origin have rather the 

 best of the argument. We have had oh the one side Cope, the 

 earlier Dollo, and Hay advocating an ancient and remote origin 

 of Dermochelys / while on the other, Baur, the later Dollo, 

 and Wieland have believed Dermochelys a highly specialized 

 descendant of true turtles, and hence of modern or relatively 

 recent derivation. That the latter of these hypotheses more 

 nearly expresses the final truth is now evident ; though both 

 contain elements of truth, and are by no means so remote as 

 they at first sight appeared to be. 



Thus, just as Dollo deserted the one camp for the other, so 

 Hay has gradually developed, not to say modified, his premises 

 to a point where they adjoin our own. "While not absolutely 

 closed, therefore, and still lacking the testimony of many forms 

 yet sure to be discovered, this famous controversy of the biolo- 

 gist as to the origin of the " leatherback " is now nearly elimi- 

 nated. Nor is it too much to say that it has proved quite as 

 fruitful throughout as the broader but scarcely more profitable 

 question of the origin of the Testudinata. 



References. 



1 — 1872. Cope, E. D. — A description of the Genus Protostega. Proc. Am. 



Phil. Soc, Phila., vol. xii, p. 422. 

 2. — 1875. Cope, E. D. — The Vertebrata of the Cretaceous Formations of 



the West. Kept. U. S. Geol. Surv. Terr., vol. ii, pp. 99-113, pis. 9-13. 



Washington. 

 3. — 1884. Capellini, G. — II Chelonio Veronese Protosphargis Veronensis. 



R. Accad. dei Lincei. 36 pp., 7 pis. Rome. 

 4. — 1889. Baur, G. — Die systematische Stellung von Dermochelys Blain- 



ville. Biolog. Centralbl., Bd. ix, p. 189. 

 5. — 1895. Hay, O. P. — On certain portions of the skeleton of Protostega 



gigas. Field Columbian Mus., Pub. No. 7 (Zool. Ser., vol. i, No. 2), 



pp. 57-62, pis. iv and v. 



