REMARKABLE TORTOISE, TESTtDO LOVEElDGIl. 505 



from the carapace by wide arches, the contact with it being 

 formed by long thin neural processes ; in no case is the main 

 column, even nai-rowly, in contact (excepting T. tornieri). 



It is in some cases impossible to detect what remains of the 

 neural arcli in a section, for it has degenerated to such an 

 extent that in some individuals it appears to be wanting 

 altogether. Possibly it is absorbed to a variable extent in the 

 same manner as the ribs. In the vertebral sections figured {vide 

 text-fig. 14), it seems to be represented by an extremely thin 

 layer beneath the neural plate, forming a meagre roof to the 

 neural canal. The specimen to which it belongs, however, is the 

 most degenei'ate of any that have been examined. More normal 

 individuals, however, cannot be spared for the necessary dissec- 

 tion. Figs, c and d show diagrams of sections through the 

 middle and towards the anterior end of the eleventh vertebra ; 



Text-fio-ure 14. 



•lift 

 iicc 



d. 



,..np.. 



Z^ 



Diagrams of niid-dovsal vertebra?, a. Anterior end. b. Posterior end. e. Section 

 towards one end. d. Section through middle. 6. Side view of vertebra? with 

 lateral expansions of nenral plates cut off. f. Two vertebrEe bent apart, to 

 shoTV thinness and flexibility of the combined neural plate and neural arch. 

 Epidermal shield, es ; dermis, d ; neural plate, nj) ; neural arch, na ; centrum, c. 



figs, a and b, the vertebra viewed from each end ; fig. e, the 

 twelfth and thirteenth with part of eleventh, side view, with 

 the lateral portion of the third neural plate cut through ; fig. f, 

 the twelfth and thirteenth, bent apart to show the thin flexible 

 covering of the neural canal. The relative positions of the 

 articulation of the vertebrae and the neural plate sutures vary, 

 usually alternating with each other. The points of juncture 

 between the 5th and 6th neural plates and 14th and 15th 

 vertebrae, however, coincide, one above the other. 



The ninth vertebra is, of course, highly specialised for the articu- 

 lation of the neck. The facets for the articulation of the first 

 (non-functional) ribs are situated a,t the extreme anterior end. 

 Vertebrae ten (2nd dorsal) to thirteen ai-e progressively more 

 elongate, and have the tubercles for the articulation of the rib- 

 heads at the extreme anterior end on each side as in the ninth ; 

 in some of the young, articulation takes place at the juncture of 

 each consecutive pair of vertebrse. Fourteenth to seventeenth 

 become progressively shorter, and the facets for the corre- 

 sponding rib move further bacliwards in a lateral ridge as the 

 ribs become dii^ected obliquely in this direction. Eighteenth 



