G. B. Wieland—On Marine Turtles. 107 



from crushing, splendid conservation of all surface features, and 

 the presence of a nearly complete series of ribs, with the 

 nuchal, the anterior neurals. and important marginals com- 

 pleting all the frontal border, the present carapace must be 

 regarded as a magnificent specimen. In fact, the only 

 structural point in the restoration here given, which awaits 

 confirmation or disproval by future discovery, is the degree 

 of development exhibited by the tenth pair of ribs. They are 

 represented free, as in Archelon in figure 2, and such ribs 

 extending out to meet the final marginal are regarded as a prob- 

 able family distinction. It may be, however, that placing 

 the proximal portion of the right fifth pleural as assigned and 

 then restoring a sixth and a seventh pleural on the leftside are 

 not warranted. In such a contingency two suppositions are, 

 therefore, open, as follows : (a) The pair of ribs shown as the 

 tenth may be really the ninth, and the true tenth pair of ribs 

 may not be present, perhaps being only slightly smaller than 

 those shown in the restoration, but passing out to meet the 

 marginals. Such being the case, the only error made is in 

 placing the pleuralia, from the fifth pair of ribs on, one number 

 too far back ; (h) An unrecovered tenth pair of ribs may be 

 reduced, as in the Oheloniidse, and may not have passed out to 

 the final marginal. In this case, the post-fifth pleuralia would 

 not only be one number too far back, but the carapace would 

 be as here represented several centimeters too long. If either 

 error has been made, the former seems by far the more 

 probable. 



The neuralia are heavier than in Protostega gigas, and 

 form a strong unbroken mid-ridge of normal Testudinate form 

 in sharp distinction to the epineural grooving and anomalous 

 structure of Archelon. Though it is to be noted that on the 

 first neural, the second and third, evidently on the fourth and 

 fifth, and probably on the missing eighth and ninth, there is 

 a strong accentuation of the mid-ridge, suggesting the appear- 

 ance seen in Toxochelys Banri. In the latter form, however, 

 this feature is due to discrete epineural ossicles, while in Pro- 

 tostega Copei there is no evidence of osteodermal elements. 

 Nor are there any hornshield groovings ; on the contrary, the 

 evidence is always to the effect that the Protostegidse were 

 enveloped in a leathery hide. 



Fortunately, the nuchal is sufficiently complete to show the 

 entire outline as a heavy normal element much as in Osteo- 

 pygis, except that a prominent nether process is present. The 

 first marginals, which are rather short and flat elements, are 

 quite complete, as is also the rather long second marginal 

 of the left side, with the distal half of that of the right side. 

 On the latter may be traced with precision, one after the other, 



