84 THE VOYAGE OF H.M.S. CHALLENGER. 



from the digital branch of the internal plantar nerve (i.p.n.), which is distributed to the 

 adjacent sides of the index and hallux. 



Edentata. 



I have examined the feet of three members of this group, viz., the Tarn andua, the 

 Armadillo, and the three-toed Sloth. They all deviate from the typical arrangement, 

 and the two last present certain features of great interest. 



Myrmecophaga tamandua (PL VIII. figs. 5 and G). 



The foot of this animal is pentadactylous ; and the toes are all of nearly equal length, 

 and each is armed with a powerful curved claw. The three layers of intrinsic muscles are 

 quite distinct, but there is a considerable reduction in the typical number of elements 

 composing the flexor layer, and abduction and adduction of the digits is not effected with 

 reference to the medius. 



Plantar layer (figs. p 1 , |> 2 , £> 5 ). — Three muscles are found in this layer, viz. : — 



1. The adductor hallucis (p 1 ). 2. The adductor indicis (p 2 ). 



3. The adductor minimi cligiti (p 5 ). 



The adductor minimi cligiti is a narrow muscular slip arising from the base of the 

 fourth metatarsal bone and the sheath of the tendon of the peroneus longus, and inserted 

 into the inner aspect of the base of the proximal phalanx of the minimus. 



The adductor hallucis and adductor indicis are fan-shaped muscles, and they take 

 origin in great part from a strong fibrous raphe which is attached by one end to the 

 tibial side of the head and by the other extremity to the tibial side of the base of the 

 fifth metatarsal bone. The adductor hallucis springs by its base from the proximal half 

 of the inner border of this raphe, and also from the ligamentous textures over the bases of 

 the third and fourth metatarsal bones. It is inserted upon the fibular side of the base of 

 the first phalanx of the hallux. The adductor indicis aiises from the distal half of the 

 raphe, and has a narrow insertion into the fibular side of the base of the first phalanx of 

 the index. 



In the left foot (fig. 5, p) an additional adducting slip for the index was found. It 

 took origin from the inner side of the base of the proximal phalanx of the minimus, and 

 stretched transversely across roots of the annularis and medius to reach the index. This 

 points to the tendency which any powerfully developed adductiug muscle has to divide 

 into an oblique and a transverse part. It is the result of the same process which is so 

 strikingly seen in the adductor hallucis of Apes and Man. 



These adducting muscles in the Tamandua, apparently act so as to approximate the 

 toes towards the annularis. The medius, however, is not provided with a special adductor. 



