1809. J TllK -Ul'OLOGl" OF THE JiUBXTATA. iOU3 



base of the outermost metatarsal. In OJwhepiis, Humphry (9) 

 found the muscle as in Bradt/pm, but in another specimen (10) as 

 well as in our own (8) it was not seen. In the Miinai'copha(jidm 

 the muscle is present in Mijrmecophaga (11, 12), Tamandua (14, 

 15), and Gyclotharus (19). In Busy pun (22 and another) among 

 the Dasypodidce the muscle rose from the outer side of the fibula 

 and from the external condyle. It is also present in Ghlamydo- 

 phonis (27, 28, 28«). In the Manidce (29, 32, 33) and Oryctero- 

 podidte (35, Sij) the muscle is present and normal. 



Peronei tertius, cpiarti et qainti diyiti. — It is dilHcuit, in 

 reviewing the literatui'e, to feel perfectly certain as to the identity 

 of these muscles. Macalister (VII.) says " there is no trace 

 whatever of a true peroueus tertius in any of the species examined, 

 Chla»iydop}wrus, Tatusia, Dasy/jus, Brady pus, OJiolcepus, Orycteropus, 

 Fholidotus, Cyclothurus, or Tamandua. The muscles described as 

 such by authors are, in reality, peronei quinti.'' We have little 

 doubt that Macalister is right in many cases, but we have some 

 doubt as to whether the statement applies accurately to all, since 

 we have seen and already described a typical peroneus 

 tertius in Brady pus. The points which, in our opinion, enable a 

 right decision to be arrived at in the case of a doubtful peroneus 

 tertius or p. quinti digiti are (a) its nerve-supply ; (h) its relation 

 to the ankle, whether anterior or posterior ; (c) its insertion into 

 the extensor tendon or into the metatarsal bone of a digit. 

 Unfortunately many writers fail to give details on some of these 

 points or on all of them, and for this reason any generalizations 

 which we may venture to offer must be taken with a reservation. 

 In the Brady podidce a well-marked peroneus tertius, inserted into 

 the base of ^the metatarsal bone, passing in front of the ankle, and 

 supplied by the anterior crural nerve, was found. Meckel (XL) 

 and Mackintosh (XVI.) mention a peroneus quinti, which the 

 latter savs is inserted into the tuberosity of the outer metatai'sal. 

 In Clioloepus (9, 10) a peroneus tertius is described, Humphry (9) 

 stating that it came from the front of the fibula and was inserted 

 into the bases of the two outer metatarsal bones. The relation to 

 the ankle is not mentioned, but from what we learn as to its origin 

 and insertion we are inclined to agree as to the correctness of this 

 denomination. It should be borne in mind that both Cholcepus 

 and Bradypus have only three toes on the hind foot ; so that a 

 peroneus quinti is not, so far as we have learnt the lessons of 

 mammalian myology, a muscle with which one would expect to 

 meet. In the Myrmecopliayida' the outer or fifth toe is always 

 developed, and we find that both Myrmecophaga (11) and Tamandua 

 (14) have a peroneus quinti digiti, but we have not been able to 

 satisfy ourselves as to the absence or presence of this muscle in 

 Cyclothurus. In the Dasypodidce the peroneus quinti is present in 

 Dasypus (22 and another) and CMamydophorus (27, 28 a). In the 

 Manidce (29, 32, 33) we find no account of a peroneus quarti or 

 quinti. In the Orycteropodidce (35, 3f!) all four peronei were 

 present, viz., longus, bre\ds, quarti et quinti digitorum. 



