436 OLIVER p. HAY 



flakes of bone which possibly correspond to the plates which 

 form the mosaic between the keels of Dermochelys. No traces 

 of the supramarginal and inframarginal keels are found. The 

 presence of the bones of the marginal keels, as shown by dis- 

 tinct sutural surfaces and by the actual bones, suffices to prove 

 that the peripheral bones of Cr5Tptodira and Pleurodira are not 

 epithecals, but belong to the same category as the costal plates, 

 the neurals and the nuchal. 



Dr. Otto Jaekel described in 1915 (Palaeont. Zeitschr., Bd. 

 2, S. 88-112) a remarkable and finely preserved turtle from the 

 Trias of Germany. He is to be congratulated on having the 

 opportunity to study such an important specimen and on his 

 results. Unfortunately, the part of the Zeitschrift which con- 

 tains the conclusion of his paper has not been received at Wash- 

 ington. Some remarks will be made here on that part at hand. 

 Doctor Jaekel named this animal Stegochelys dux; but, inas- 

 much as this generic name was preoccupied, he later proposed 

 instead the name Triassochelj^s (Abel, Die Stamme der Wir- 

 beltiere, 1919, pp. 386-392, figs.) 



In case Doctor Jaekel means, as he doubtless does, that he 

 has been able to furnish corroborative evidence that the plastron 

 of the Testudinata is composed of the clavicles and the inter- 

 clavicle and of abdominal ribs (gastraUa), his statement is read- 

 ily accepted; but certainly there was previously Httle doubt 

 about its composition. The present writer in 1898 (Amer. 

 NaturaUst, vol. 32, p. 934) assumed this view and made no claims 

 of originality therefor. In the writer's paper referred to, he 

 attempted (p. 946) to determine the number of gastraUa that had 

 entered into the formation of the plastron. This number, three 

 or four pairs, is indeed small; and naturally, in case the num- 

 ber recorded by Jaekel, about twenty-five in each of the 

 anteroposterior rows, is confirmed, the writer's calculations will 

 be discredited. 



The type of Triassochelys was evidently a fully mature, prob- 

 ably an old animal; and, like many of the ancient testudinates, 

 it appears to have had most of the various bones of the shell 

 thoroughly coossified. With the exception of the sutures between 



