G. B. Wieland — On Marine Turtles. 331 



ogy of the osteodermal mosaic of Dermochelys (6, 7). The 

 present is, however, the first time that the entire series of 

 ossicles and their relation to the successive nenrals has been 

 determined. As may be judged from reference to the several 

 figures, the system of ossicles may really be a much changed 

 and disappearing one. The first neural bears a small but very 

 distinct completely fused boss near its middle, and then forms 

 the beginning of the dorsal carina. The third neural which is 

 rather short, and the fourth which is abnormally long, support 

 a large epi-neural spine. This occupies all the median poste- 

 rior three-fourths of the length of the third and the anterior 

 fourth of the length of the fourth neurals, and is doubtless the 

 second member of the original epi-neural series. The second 

 free epi-neural [or third of the original series] is the largest, 

 and is equally borne by the fifth and sixth neurals. The third 

 free epi-neural [or fourth of the hypothetical primitive series] 

 rests over the ninth member of the neuralia, so as to project 

 slightly forward onto the eighth and well backward over all 

 the anterior half of the post-neural tenth. This latter epi- 

 neural is the smallest of the three free epi-neurals. 



Figure 4. — Toxochelys Bauri type, x 1 /]. a, Vertical transverse section 

 through the second neural showing the average elevation and outline of the 

 median neural carina, b, Vertical transverse section through anterior end of 

 the 6th neural, and the epi-neural spine (s) borne on this and the 5th neurals. 



Whether a fifth member of the epi-neural series was borne 

 by the postero-pygal, which would afford the symmetrical posi- 

 tion, is of course conjectural in the absence of this latter 

 member of the median series. 



