REPORT ON THE MARSUPIALIA. 103 



Hyracoidea. 



Hyrax capensis. 



The foot of the Hyrax is triclactylous — the hallux and minimus being absent. Of 

 the three remaining digits the index alone possesses the three typical intrinsic muscles, 

 whilst the medius and annularis each want an abductor. The myology of this interesting 

 animal has been very fully worked out by Messrs. Murie and Mivart. 1 Even the minute 

 intrinsic pedal muscles have not escaped their notice. They make no attempt, however, 

 to classify these muscles, but merely describe them as single and double interossei. Their 

 description is so accurate and exact that, in so far as the attachments of the muscles are 

 concerned, I have little to add. 



Plantar layer. — This layer is composed of two muscles, viz. , (l) adductor indicia, and 

 (2) adductor annularis. By Murie and Mivart they are named the second and fourth 

 single interosseous muscles. In the figure which illustrates their description these 

 muscles are represented as arising far apart from each other, and as being on the same 

 plane as the other muscles. This is not the case, because proximally they are in contact 

 and superficial, and they only diverge as they are traced towards their insertions. The 

 adductor indicis arises from the fibrous structures on the plantar surface of the scaphoid 

 bone, and is inserted into the fibular aspect of the base of the first phalanx of the index. 

 The adductor annularis springs from the ligamentous tissue on the under surface of the 

 cuboid, and is inserted into the tibial side of the base of the first phalanx of the 

 annularis. 



Intermediate layer. — Each digit is provided with a two-headed flexor brevis which 

 lies upon the plantar aspect of the corresponding metatarsal bone, and has the usual 

 connections ; these muscles are termed by Murie and Mivart the double interossei. 



Dorsal layer. — This group is only partially represented, the first and second dorsal 

 interossei alone are present (first and third single interossei of Murie and Mivart). 



The first dorsal interosseus or abductor indicis is a powerful muscle which arises 

 from the inner and dorsal surface of the second metatarsal bone in its proximal half, and is 

 inserted into the tibial side of the base of the first phalanx of the index. 



The second dorsal interosseous muscle is not so strongly marked. It arises from the 

 plantar aspect of the base of the middle metatarsal bone under cover of the adductor 

 indicis, and is inserted into the inner aspect of the base of the first phalanx of the medius. 



No trace of the two absent dorsal interosseous muscles is to be found. In all proba- 

 bility the third has coalesced with the outer head of the flexor brevis medii, and the fourth 

 with the outer head of the flexor brevis annularis. 



Messrs. Murie and Mivart noticed in their specimen muscular fibres arising from a 

 ligamentous fascia upon the outer surface of the os calcis, and inserted into the head of the 



1 Proceedings of the Zoological Society of London, 1865, pp. 351, 352, 353. 



