502 MISS JOAN B. PROCTER ON THE 



vertebral shields and proceeding backwards almost to the eighth 

 neural. 



Presumably this fenestra and the small oval one between the 

 seventh and eighth costals are all that remain of the large kidney- 

 shaped one, similar to those between the preceding costal and 

 neurals, which is pi-esent in youth. 



The marginal bones are somewhat wider than the corresponding 

 shields ; first, second, and third markedly so ; sixth to tenth deeply 

 notched in the middle for the reception of spurs from the corre- 

 sponding costal plates. Fifth, sixth, and seventh enter into the 

 composition of the plastron beneath, and will be dealt with as 

 part of the plastron. 



When one considers the great depth of the lateral marginals 

 in ordinary tortoises in comparison with their abnormal shallow- 

 ness in T. loveridgli, the shallow carapace of the latter is to 

 some extent explained. In text-fig. 11 the fifth, six, and seventh 

 marginal plates, drawn diagrammatically, of T. loveridgii and 

 T. ibera are compared. 



The bony plastron of the adult. 



The bony plastron is also composed of bone thin to trans- 

 lucency. In the centre there is an enormous diamond-shaped 

 fenestra reaching from ento- to xiphiplastron, and side to side 

 from marginals to marginals. It is very ragged in outline, 

 variable in size, and lies beneath the pectoral and abdominal 

 shields, so that the greater part of the abdomen is unprotected 

 by bone {vide text-fig. 12). 



Epiplastrons (ep.) shapely, oblique, moderate in size; posterior 

 bordei-s serpentine. 



Entoplastron {ent.) in the shape of a diamond, the anterior and 

 posterior corners of which have been truncated ; posterior margin 

 free, corresponding with the humero-pectoral shield-suture above, 

 entering into the central fenestra, into which a sharp bony spur 

 projects, representing the tip of the sternum, which is fused to the 

 inner surface of this plate in the normal way. 



Hyoplastrons (Ap.) very small, rectangular, obliquely set ; 

 separated from each other by the anterior angle of central 

 fenestra; widely separated from the hypoplastrons by marginal 

 plates. 



Marginal plates {mp.) 5, 6, and 7 enter into the composition 

 of the plastron on each side of the fenestra, spreading obliquely 

 invvards to a most unusual degree, number 5 running beneath the 

 pectoral shields to the abdomiiial, and terminating with a free 

 oblique edge in the central fenestra ; number 6 borders the lateral 

 corner of the centi'al fenestra on each side. 



Hypoplastrons {hyp.) completely separated from each other by 

 the posterior angle of the central fenestra ; produced to form 

 pq-rt of the posterior plasti'al lobe. 



