120 



G. R. Wieland — On Marine Turtles. 



and forward ; for even in that portion of the outer border next 

 to the humeral notch there are blunt spines. 



Did the spines of the marginals articulate with one or more 

 carapacial and plastral rows of dermal ossifications, and thus 

 afford the nearest approximation to the osteodermal mosaic of 

 Dermochelys yet discovered by adding dermal ossification on all 

 the keel lines, that is the neural keel, the pleural keel, the supra- 

 marginal, and marginal 



keel! 



I 



Figure 10. — Archelonischyros x^. 



A large 

 dermal ossicle found in connection with the 

 plastron of the original type, but possibly 

 dorsal. O, the outer view ; S, sectional view 

 showing the extreme thinness of the element. 

 Note that the asymmetry of this element and 

 its dactylate border indicate not only connec- 

 tion with other dermal elements, but the 

 probability of the presence of entire series of 

 such elements. 



believe such to 

 be the case, for at least 

 tw T o elements referable 

 to a similar additional 

 series corresponding to 

 the supra-pleural keel of 

 Dermochelys have been 

 recovered. Nor is it 

 strange that more have 

 not been obtained. A 

 fine shark's tooth per- 

 taining to a scavenger 

 species related to Lam- 

 na was found with the 

 type, and clearly indi- 



cates that all dermal por- 

 tions loosely affixed to 

 other elements of the 

 carapace or plastron 

 must have been pecu- 

 liarly liable to disassocia- 

 tion. In what other than a supra-marginal or infra-marginal 

 position is it possible to place the thin and distinctly asym- 

 metrical element shown in figure 10 ? It represents an 

 integral part either of the carapace or of the plastron. Further, 

 the likewise unique element shown in connection with the 

 marginal in figure 11 can not be interpreted as in other 

 than a natural position. From the fact that it is digitate all 

 around and slightly asymmetrical, it may be inferred that a 

 series of such elements lay inside of, and articulated with, the 

 superior borders of the marginals, alternating quite regularly 

 with them in about a double number, and that beyond this 

 space a second much thinner supra-marginal series was present. 

 The space between the latter and the midline of the cara- 

 pace, where, as has been already seen, the presence of a median 

 row of supra-neural or in part osteodermal elements is demon- 

 strated, may or may not have been continuously occupied by 

 ossifications. In any event, there are the seven dorsal keels, 

 as in Dermochelys. On the plastral side, direct evidence of 



