•572 Correspondence — Prof. E. D. Cope. 



than the higher, or else two distinct series ; and he inclines to the 

 latter view. Both, however, must be separated from the Laurentian 

 by a great interval of time, and neither exhibits metamorphism 

 comparable with that of a series of schists and gneisses, like the 

 so-called Montalban. The newer reminds him often of the English 

 Pebidians. 



ooiai^iEsipoisriDiBiNroEi. 



LYDEKKER, BOULENGER, AND DOLLO ON FOSSIL TORTOISES. 



Sir, — I have read with interest the notes on the above subject 

 which appeared in the Geological Magazine for June and September, 

 I find that the two first-named gentlemen have overlooked a paper of 

 mine, which will relieve me of the charge of erroneous treatment of 

 the genus Pleuro sternum which they make. The paper was published 

 in 1870,^ and pi'ior to those of Professor Eiitimeyer which they cite 

 as authority for determination already made by me. The learned 

 authors quote me as stating that in the genus Pleiirosternwn there is 

 ■^'no intergular shield, and the genus is accordingly referred by me 

 to the Cryptodira ; whereas its true position, as was pointed out by 

 Prof. Eiitimeyer, is with the Pleurodira ; and with that group — the 

 Pelomedusidee and Peltocephalid^ of Gray — characterized by the 

 presence of eleven, instead of nine, plastral bones." On a subsequent 

 page (274-5) they consider the Platemys Bowerbankii, of Owen and 

 Bell, " in regard to which Prof. Kutimeyer has already pointed out 

 that the specimen figured by the same writers under the name of 

 Emys IcBvis is merely the young of the former, and that owing to 

 the presence of a small mesoplastral bone, the reference to Platemys 

 is incorrect, and it is suggested that tlie species may probably belong 

 either to Podocnemis or PeJlocephalus." ^ 



In my paper of 1870 I remark, "The genus Platemys as adopted 

 [in Maack's work] may be cited. It embraces nine species according 

 to the present work, the genus Pleurosternvm of Owen being referred 

 to it. This is done because the additional pair of thoracic bones 

 which characterizes it is found in a rudimental condition in Platemys. 

 Bowerhankii ; and Platemys BuUoclcii of Owen presents the inter- 

 marginal scuta of Pleurosternvm, and because of the general 

 resemblance in specific characters between the latter and the PI. 

 concinnum. To us, however, the genus Pleurosternum appears to be 

 Cryptodire, not Pleurodire, as it lacks the intergular scutum of 

 the later suborder, and to represent a peculiar family of that group 

 characterized by the possession of ten instead of eight sternal bones. 

 Platemys Bullockii, P. Bowerbanhii, and Emys Icevis, Owen and Bell, 

 appear on the other hand to be Pleurodira, and to be referable to 

 two families of that suborder. The PL Bullockii, on account of its 

 five pairs of sternal bones, to the Sternoth£erida3, and on account of 



^ Die bis jetzt bekannten Schildkorten, u. d. bei Theilheim in Hannover neu 

 afgefunden altesten Arteu derselben ; von Dr. G. A. Maack ; a review by E. D. Cope, 

 Araer. Journal Sci. Arts, 1870, L. pp. 136. 



■■^ " The figure shows tliat its affinity appears to be rather with the former than the 

 latter, and it may accordingly be provisionally referred to that genus." 



