o/" Cyclothiirus didactyliis. 263 



of tlie liiiihs of the Slotlis appears to be fairly applicable 

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

 ticfe corj)oris partis esse, posticam vero validis musculis ad 

 auteriorem attrahi atqiie hujus motus sequi debere," — and the 

 more so when we contrast the short humerus, rugged with 

 strong muscular ridges, Avith 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 (PL 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 ninuerous 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 YIILf 



F!(/. 1. JRig'lit fore foot, inner side. 



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



Fiff. 3. Eight hind foot, inner side. 



Fiff. 4. Plantar surface of the same. 



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



left side. 



Fiff, G. Dorsal view of carpal and metacarpal bones, right side. 



Fiff. 7. Palmar aspect of the proximal row of the carpal bones, left side J. 



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

 instrimient ii.*ed by the Eomans when perspiring in the bath : hence the 

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

 name, may call it stri(iiUfon)i. Meckel considered that it was probably a 

 homologue of the bone which carries the spur in the Ornithorhynchus ; 

 and Cuviei", in his ' Ossemens Fossiles ' (nouvelle edit. Paris, 18i'3, tome v. 

 l*'* partic, p. 108), makes the following remarks relative to its probable 

 function : — " Un os surnumt5raire articule siir le cuneiforme interne, et qui, 

 dans le Tamauoir, le Tamandua, et les Pangolins, est triangulaire et fort 

 petit, rnais qui, dans le petit Fourniilier, s'allonge et s'elargit de maniere 

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

 est extraordiuairement court, ne se portant point en arriere plus que 

 I'astragale lui-meme. Cet os surnumeraire est ce qui donue ii la plante 

 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 Eoyal College of Surgeons. 



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

 but wa'* single on the right side of the skeleton, and on both sides in the 

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

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

 osseous centres, is a doubtful question. 



