NO. 1669. NEW SPEVIEH OF LEATIIERBACK TURTLE— PALMER. 37^ 



touched hy the fingers; usually with a small pit near the center. 

 Scutes of the outer and posterior edges much smaller and thinner 

 than the others, and very similar to those of D. corlacea. Scutes of 

 the plastron quite thick and smooth, with well-rounded outlines; 

 those of the edge forming an undulating line. (Plate 31, fig. F.) 



Among the best-preserved bones there is the upper half of a verte- 

 bra which is nearly perfect. It differs from a similar vertebra in 

 D. coriacea principally in the size of the articular surface for the ribs, 

 which is very much larger than in that species. Several pieces of 

 ribs are also very similar, but one piece (fig. .4), perhaps a tip, has 

 very fine striations on its curved side and is smooth and reddish 

 brown in color. The bones are light and very porous, and, conse- 

 quently, many of the more prominent surfaces are badly disinte- 

 grated, a condition evidently due to the seepage of water through 

 the stratum in which they were embedded. 



On comparing our specimens with the excellent plate of the iy\)Q- 

 material of P. folygonus in Professor Seeley's paper," and with a 

 cleaned specimen of the carapace of D. coi^icea in the National 

 Museum, the differences in the ridges and shapes of the scutes were 

 very evident. The scutes of the anterior median portion of the cara- 

 pace are distinctly different in the three species, but as the outer and 

 posterior edges are reached the scutes of the three species becom.e 

 quite similar. The large, thick scutes composing the anterior por- 

 tion of the median ridge in P. calvertensis differ decidedly from 

 similarly placed scutes in the other species. In our specimen, the 

 ordinary scutes are flat above or nearly so, and their edges are not 

 raised, so that the surface of any two adjoining scutes is continuous. 

 In the lateral ridges, the rows of rai.sed scutes are but slightly thick- 

 ened and rounded along the middle (fig. D), and there is a tendency 

 toward a parallel arrangement of adjoining scutes. Many of the 

 separate scutes, as well as the larger pieces, are much waterworn and 

 otherwise injured. It is possible that the surface was more distinctly 

 sculptured originally, and that the sculpturing has been eroded. 



Professor Seeley writes'' that Von Meyer (1851) pointed out the 

 striking resemblance of the carapace of P. pohjgonus to one from 

 the zeuglodont limestone of North America which ^liiller had figured 

 and compared Avith the dorsal shield of Dermatochelys [= Dcrmo- 

 chelys] in his work on Zeuglodon. On comparing our material with 

 Miiller's excellent figure, it seems evident to me that his specimen was 

 a part of a plastron, agreeing closely with ours in the size, shape, 

 and general appearance of the scutes. The dominant, or more char- 

 acteristic, scutes of these three species differ from each other decid- 



« Quart. Journ. Geol. Soc, London, 36, 1880, p. 40G, pi. 15. 

 6 Idem, p. 407, 



