REMARKABLE TORTOISE, TESTUDO LOVERIDGII. 521 



(a) Wliei^e this takes place concentricaily, as seen by such 

 striations in the epidermal shields, the plates in the early stages 

 of development are localised principally beneath the shield- 

 sutures, as in Testudo, Ginixys, etc. 



(h) Where growth is uniform throughout each area, develop- 

 ment of the plates is also equalised, proceeding from the individual 

 centres of ossification, as in Emys etc. 



Summary. 



Testudo loveridgii has an excessively depressed soft-shelled 

 carapace, and is able to inflate itself to a certain degree. It 

 possesses a bony carapace and plastron, but they are extensively 

 fenestrated, incomplete, and similar in essentials to the juvenile 

 stages of other species. 



Marginal plates five, six, and seven spread inwards in a unique 

 manner, entering into the composition of the plastron and 

 separating the hyo- and hypoplastrons from each other. Their 

 upper portions are extraordinarily shallow. 



The ribs in T. loveridgii become (usually) entirely absorbed, 

 apparently by the osteoclasts Avhich are present beneath the 

 periosteum. A simulacrum of the capitular portion, soft like 

 ligament, and formed chiefly of periosteum, persists for some 

 while. 



The neural arch is vestigial and sometimes completely wanting, 

 the neural plates being applied to the depressed centra to form 

 the roof of the neural canal. Absorption probably takes place to 

 some extent as in the ribs, but the arch is never more than a 

 simple layer of bone, without spinous processes. 



The jaws, together with their investing horny sheaths, are 

 denticulated with remarkable regularity. 



Fenestration in this and other species is caused by arrested 

 development, and not, as previously supposed, by absorption with 

 age. 



The development of the hony plates in T. loveridgii and the 

 young of other species points to the neurals and costals being of 

 dermal origin. The principal evidence is : — 



(1) That they are developing whilst the ribs and neural arches of 

 the tru,e skeleton are degenerating. (2) That the point of origin of 

 each costal plate is alternately nearer to and further from the rib 

 capitulum. (3) That the form of these plates in their early stages of 

 development is in strict correlation toith the bor^ders of, or sutures 

 between, the superincumbent epidermal shields. 



It seems possible that the development of the plates is regulated 

 by that of the areas of dermis corresponding to the epidermal shields ; 

 (1) forming a netiuork as in T. loveridgii and other species lohen 

 this groioth proceeds concentrically, or (2) proceeding equally from 

 each centre of origin where dermal growth takes place equally within 

 each area as in Emys etc. 



