128 G. E. Wieland—On Marine Turtles. 



A. ischyros (type) P. gigas (cotype)* 



Extreme length of coracoid 75 ,cm . _ . . 4o- cni 



Procoraco-scapular length 66* 30' 



Median line to tip of second 



rib 100- 



Extreme length of humerus 60- 



Length of ten dorsal centra 127' 



Extreme length of femur 49- 



a 



■<->■ 



tibia 33 



fibula 3] 



radius 30 



ulna 35 



56 



34 

 .68 



27 

 .20 

 .20 



20 

 .17 



Concluding Remarks. 



Not only will future field work reveal new members of the 

 Protostegidse of the greatest interest, but quite all the skeletal 

 features now in doubt must certainly be clearly observed as one 

 specimen after another is collected. Indeed it can be freely 

 predicted that but a very few years will be required to accumu- 

 late the material demanding a second revision. 



Meantime it must be left to such further discovery to deter- 

 mine, among various other features, what the exact condition 

 of the neural line of JProtostega gigas really is, and whether 

 this species and P. Copei do not really belong to separate 

 genera ; for there is a distinct suspicion that the species of 

 Protostegidse already known may really include a third genus. 

 Evidently the marked difference in the structure of the cara- 

 pacial midline between Archelon and Protostega Copei indi- 

 cates a condition promising variations of the most striking and 

 interesting character, to say nothing of the possibility of variety 

 in the dermogene elements on the lines of the keels. These 

 should very clearly be named in both Dermochelys and 

 other turtles, the neural, pleural, supra-marginal, and marginal 

 keels above, and the infra-marginal, hyo-hypoplastral, and the 

 nether median or epi-xiphiplastral keels below. 



It is not presumable that there is any doubt as to the pres- 

 ence of broad generic distinctions between Protostega gigas and 

 Archelon, although the midline of these two forms may prove 

 to be much more nearly similar than we now suppose. It is, 

 however, a very striking fact that Protostega Copei and P. 

 {Archelon) Marshii are both so much more nearly normal in 

 their carapacial structure than is Archelon. This is to say, 

 normal when we have in mind the great majority of turtles 

 with normal neuralia such as the early Protostegids are shown 

 to have. One might indeed suspect it possible from the strong 



*This is the splendid specimen, No. 1421, of the Carnegie Museum, 

 Pittsburg. 



