G. B. Wieland — On Marine Tur 



337 



of the present T. jBmiri, as may be noted on comparison with 

 a nuchal figured by Case.* 



Nor is there specific agreement with the nuchal of the Yale 

 specimen I referred to, T. latiremis, when describing the 

 accompanying flipper (10). This nuchal is here shown in 

 figure 8 for the sake of more convenient reference. 



Figure 8. — Toxochelys latiremis, from the Niobrara Cretaceous, Gove 

 County, Kansas. (Yale accession list 2419.) x about %. 



Nuchal with the attached first marginals of both sides and the proximal 

 half of the right second marginal, together with the accompanying epi- 

 plastron. — This nuchal bears far back nearly in line with the front border 

 of the large curved posterior notches a large and prominent nether process 

 for cervical articulation. 



Although true that the general form varies in turn from 

 that just noted as figured by Case, the differences are more 

 easily reconciled within specific limits. The simple fact is 

 that in no previously described specimen of Toxochelys, and 

 in no other semi-marine, or marine member of the Cheloniidse, 

 do we observe Trionychid-like foramina between the nuchal 

 and first neural and pleurals. 1 may add that from recent 

 measurements given by Hay it appears that amongst the 

 several Toxochelyds T. orachyrliinus is next related to T. 

 latiremis ; and there is a question in my mind if the former 

 is a distinct species, the differences in cranial proportion from 

 T. latiremis being so slight as to be of very doubtful signifi- 

 cance in specimens so invariably crushed at more or less vary- 

 ing angles as are the Niobrara fossils. 



With the skull fragments and crushed [9th] left marginal 

 of T. serrifer as recently figured for the first time by Hay (8), 

 I am unable to identify the present handsome specimen. As 

 the horn-shields of T. serrifer formed a very deep marginal 

 notch leading into a pronounced sulcus (as indicated by Hay), 

 there appear to be distinct differences. It is, of course, one of 

 the difficulties of vertebrate paleontologists that species based 



* University Geol. Survey of Kansas, pi. lxxxii, figure 3. 



