182 



A. LEITH. ADAMS ON MALTESE LAKD-TOKTOISES. 



Radius. 



This bone is represented by two specimens from Zebbug. The 

 one is about a fourth part longer than the other ; they agree, how- 

 ever, in every determinable particular ; so that, admitting variability 

 in size according to sexual and individual peculiarities, it seems 

 probable that they belonged to the adult male and female of T. 

 robusta. 



The larger (Plate YI. fig. 1) has lost a portion of the outer aspect 

 of the head and a fragment of the distal extremity ; but fig. 2, also 

 belonging to the left forearm, is quite entire. 



The dimensions of these bones, as compared with one another and 

 with the large Galapagos tortoises described by Giinther *, are as 

 follows : — 



Length of radius 



Least girth of radius 











*o 







*0 





CO 



*o 



04- 



a 



*o 





a 



?3 





e 



§ 

 e 



CO 





■■sT" 











Si 1 



•<s> 



5> 



^> 



Eh' Eh 



E^ 



Eh 



Eh" 



millim. niillim. 



millim. 



millim. 



millim. 



156 



110 



149 



122 



121 



76 



58 



51 



49 



50 



These measurements at once demonstrate the greater thickness in 

 T. robusta of the shaft as compared with the length, the girth of 

 even the smaller being greater than obtains in any of the more 

 gigantic recent species. 



Other comparisons as regards the articular surfaces furnish equally 

 interesting results. As compared with the radius of the immature 

 female of T. elephantopus referred to by Giintherf (No. 1011 of the 

 Cat. Mus. E. Coll. Surgeons), the smaller radius (fig. 2) is pre- 

 cisely of the same length, whilst the girth, midshaft, of the recent 

 bone is 43 against 58 millims. of the smaller T. robusta. 



The dimensions of the extremities of the Galapagos radii are not 

 given by Giinther ; but the typical radius of T. ephippium now be- 

 fore me furnishes the following comparisons with the two radii of 

 T. robusta : — 



* Op. cit. p. 280. 



t Phil. Trans, vol. ckv. p. 261. 



