THE EXTREMITIES OF ORYCTEROPUS CAPENSIS. 001 



into which the third tendon divides. The fibular branch of the third tendon, after 

 joining the expansion over tin metal ;irso-phalangeal joint of the fourth di it, was con- 

 tinued also to the terminal phalanx of this digit. 



The fourth tendon passed to the terminal phalanx of the fifth digit, after joining tin 

 expansion over the metatarso-phalangeal articulation. This tendon may, possibly, take 

 some share in forming what I have termed the fibular branch of the third tendon, but 

 which Prof. Humphry describes as the tibial branch of t lie fourth '. 



Each of the tendons of the extensor* communis had, at its metatawo-phalangcal expan- 

 sion, a patella-like sesamoid bone developed in it, u I rich bom s appear to belong strict 1\ 

 to the deep layers which find attachment at the base of the middle phalanges of their 

 respective digits. 



These bones do not appear to have been present in the specimen examined by I'rof. 

 Humphry. Many of them are preserved in the skeleton of Orcyteropus in the Museum 

 of the Royal College of Surgeons. A similar sesamoid, developed in a similar position, 

 is present in the terminal tendon of the extensor halluds. 



Extensor brevis dlgitorum. — This muscle arose from the outer aspect of the caloaneum, 



superior to the origin of the abductor minimi digiti — al-o from the anterior portion of the 



bone, especially the tubercle which articulates laterally with t\\^ astragalus. It then 

 passed obliquely forwards to be inserted into the inferior aspect of what I have termed 

 the "fibular" division of the tendons of the extensor communis. It also joined, by 

 means of two strong tendons, the tibial side of the second tendon and the fibular side of 

 the first tendon respectively, of the above division, just before those expand over the 

 metatarso-phalangeal joints of their proper digits — an arrangement which evidently 

 favours the approximation of the second and middle digits, which are not bound together 

 so closely as their hornologues are in Dasypus by skin and subjacent tissue. 



Another portion of the muscle is inserted fleshy into the first tendon at the point 

 where it gives off the lateral branch to the tendon of the < tensor hallncis. The extensor 

 brevis does not appear to enter into any direct communication with the fourth tendon of 



the common extensor. 



Prof. Humphry 2 describes this muscle as possessing three tendons; but the only 

 distinct offsets deserving the term, in the animal which I examined, were those described 

 as passing to the extensors of the second and middle digits. 



Abductor minimi digiti. — Fairly developed. It is a flat muscular band, which takes 



b 



from the smooth outer face of the calcaneal process, just below the origin of 



preceding muscle, and has a broad fleshy insertion into the tubercle at the outer side of 

 the base of the metacarpal bone of the fifth digit, and is also continued as a tendon to a 

 sesamoid bone lying at the base of the proximal phalanx of the same digit. 



Flexor brevis digiti quinti (Henle 3 ). — This muscle arose slightly from the calcaneum, 

 but principally from that portion of the plantar ligament which was inserted into the 

 base of the metatarsal of the fourth digit. It gradually widened towards its termination, 

 and had a fleshy insertion into the base of the proximal phalanx of the fift h digit. 



Prof. Humphry makes no mention of this muscle as existing in his specimen. 



Opponens digiti quinti (Henle).— This muscle, described by Prof. Humphry 4 under the 



1 hoc. c'U. p. 317. * hoc. at. p. 318. * Muskcllclire, p. 801. * Uc. cit. p. 317. 



4o2 



