334 G. R. Wieland—On Marine Turtles. 



common eighth and ninth elements, or better a division of the 

 ninth or post-neural region of the median series. Unlike 

 Har delta, however, the pygal is not single, the post-neural 

 region being divided into an antero- and postero-pygal, as in 

 Osteopygis, and in the Cheloninse. The existence and outlines 

 of the postero-pygal are indicated by the conformation of the 

 pleuralia and posterior marginals, together with the posterior 

 suture of the antero-pygal and the anterior suture of the pygal 

 marginal, which are quite unlike. From these sutural borders 

 it is also quite evident that the heavy median keel which 

 evenly traverses all the length of the antero-pygal, finally ran 

 out on the postero-pygal, where it no doubt ended as a distinct 

 boss like that of the first neural, which would perforce repre- 

 sent a fused fifth member of the median or epi-neural ossicular 

 system. The pygal marginal, in correspondence with the 

 strong keels of the marginals, is ornately double-keeled. The 

 organization of this region has not hitherto been determined 

 in any species of Toxochelys. Both Case (2) and Hay (6) have 

 figured the posterior half of the carapace of T. (serrifer) steno- 

 porus type, but without determining the sutures, whether 

 because not indicated or because of difficulty of interpretation 

 not being stated by either. A distinct difference from the 

 present specimen is, however, obviously present in the postero- 

 pygal region. 



Synopsis of the Characters of Toxochelys Bauri (type). 



Carapace. — Elliptical to elongate in outline with large and 

 persistent pleuro-marginal fontanelles ; composed of 52 bony 

 plates and 3 additional epi-neural spinose ossicles ; numerical 

 arrangement of parts combining the general alignment and 

 form seen in the Chelonine Lytoloma angtista with the post- 

 neural arrangement of the existing Hardella thurgi. Surface 

 finely granulate to smooth, and horn-shield sulci not apparent, 

 save for notches formed by the posterior border of the mar- 

 ginal keels. (A distinctly leathery hide is not, however, sup- 

 posed to be present.) Marginals, 11 pairs, rather narrow 

 anteriorly, increasing very slowly in breadth to the 11th, which 

 is still nearly twice as long as broad, outer borders all the way 

 to the pygal marginal more and more sharply keeled anterior 

 to the indistinct to absent horn-shield sulci, upper and nether 

 surfaces of nearly equal area, supported by rib-ends only with 

 the pits of the plastral digits small to indistinct and extending 

 from the 3d to about the middle of the 7th ; rib-pits small, 

 with the 10th marginal ribless, and the 11th supporting the 

 9th rib anteriorly as in Chelone and Lytoloma. 



Nuchal large and very broad, uniting by straight sutures 

 with the 1st neural and 1st pleurals, between which are formed 



