222 NATURE-STUDY REVIEW [10:6— Sept., 1914 



theory hardly seemed tenable. Indeed, I was quite at a loss to 

 imagine what might have been the origin of such a pectiliar hump 

 on the back of this chelonian. 



On the loth of August, 19 13, I killed the specimen with chloro- 

 form, death taking place, apparently, in a very few moments. I 

 immediately parted, longitudinally, the bridge connecting the 

 carapace and the plastron on the left side, as shown in Figure i. 

 The lungs and viscera were gently pushed to one side — all of them 

 being in a perfectly healthy and normal condition — whereupon the 

 ventral aspect of the carapace forming the dome of the hump was 

 exposed. Beyond this being uniformly concave in conformity with 

 the external convexity on the back, there was absolutely nothing 

 present to account for the enlargement. All the osseous structures 

 were healthy and exhibited no distortions of any kind beyond all 

 entering, each in due part, into the formation, as far as it extended, 

 of the concavity present. 



In other words, this deformity was congenital, and must have 

 been present when this turtle first emerged from its egg\ but to 

 account for its presence, in the light of what has been shown above, 

 is another matter, and this very interesting problem I am quite 

 unable to solve at the present time. As shedding light upon certain 

 questions in embryology, its solution may be considered important 

 from several points of view. 



These turtles, when young and up to a certain age, are quite 

 circular in outline, if viewed from above or below (Fig. 4) ; but 

 they gradually assimie the ovoid form as they mature, while at the 

 same time they usually lose entirel}^ the variegated markings on 

 the plastron, which are nearly always present in the young (Fig. 3). 

 Their wonderful beauty in the matters of form and coloration can 

 only be fully appreciated by seeing the living specimens; photo- 

 graphs give but the correct idea of their external morphology. 



