o/" Cyclothurus didactjlus. 263 



of the limbs of the Sloths appears to be fairly applicable 

 to the Two-toed Anteater, namely, " Vires motrices an- 

 ticse corporis partis esse, posticam vero validis musciilis ad 

 anteriorem attrahi atque hujus motus sequi debere," — and the 

 more so when we contrast the short humerus, rugged with 

 strong muscular ridges, with the long smooth femur, which 

 lacks even a rudiment of a third trochanter. 



In addition to a long prehensile tail (at best but a stunted 

 member in the sloths), naked for the lower third of its length, 

 the fore and hind feet (PI. VIII. figs. 1 to 4) are marvellously 

 modified for arboreal progression, the functional absence of the 

 pollex being compensated for, as Meckel hints (Archiv, p. 48), 

 by the enormous development of the pisiform bone (figs. 5 to 8), 

 to which are attached numerous strong muscles, while a long 

 strigil-shaped bone* (fig. 11), passing backward from the 

 scaphoid, more than makes up for the comparative shortness of 

 the calcaneal process. 



EXPLANATION OF PLATE VIILt 



Fi;j. 1. Right fore foot, inner side. 



Fif/. 2. Foreshortened pahnar view of the same. 



Fi(f. 3. Right hind foot, inner side. 



Fig. 4. Plantar surface of the same. 



Fig. 5. Dorsal view of radius and ulna and proximal row of carpal bones, 



left side. 

 Fig. 6. Dorsal view of carpal and metacarpal boues, right side. 

 Fig. 7. Palmar aspect of the proximal row of the carpal bones, left side:]:. 



* This bone, termed " schaufelfcinniger " by Meckel, is not unlike the 

 insti'ument used by the Romans when perspiring in the bath : hence the 

 name which I have applied to it. Those who prefer a long Latinized 

 name, may call it strigiUform. Meckel considered that it was probably a 

 homologue of tlie boue which carries the spur in the Oruithorhynchiis ; 

 and Cuvier, in his ' Ossemeus Fossiles ' (nouvelle edit. Paris, 1823, tome v. 



petit, mais qui, dans le petit Fourmilier, s'allonge et s'elargit de maniere 

 a former une sorte de talon ; il est vrai que dans cette espece le calcaneuim 

 est extraordinairement court, ne se portaut point en arriere plus que 

 I'astragale lui-meme. Cet os surnumeraire est ce qui donne a la plaute 

 du pied du petit Fourmilier cette forme concave qui la rende si propre a 

 embrasser les branches et a grimper aux arbres." 



t The figures of bones are taken from a non-articulated skeleton, 

 somewhat imperfect, belonging to the Royal College of Surgeons. 



X The OS lunare on this side was divided into two bones of equal size, 

 but was single on the rijiht side of the skeleton, and on both sides in the 

 specimen which I dissected. Whether this division be due to a fracture, 

 •which is improbable, or be the result of a development fi-om two distinct 

 osseous centres, is a doubtful question. 



