Hutton and Coughtrey. — On some Moa Remains. 269 



Anatomical Notes on the Hod's Leg found at Knobby Ranges in the 



Province of Otago. By Milled Coughtrey. 



It is the right leg, and is composed of the following bones held together by 

 muscles and ligaments : — K. tarso-inetatarsus, and bones of 1st, 2nd, 3rd, and 

 4th toes ; in addition a calcaneo-sesamoid bone at the tibio-tarsal joint, and a 

 sesamoid cartilage at the metatarso-phalangeal joint. 



The joints, sesamoids and muscles, even though fragmentary, in an extinct 

 bird must be of interest, and I will therefore describe them with care. 



Tibio-tarsal joint, i.e., the joint between distal end of tibio-tarsus and proximal 

 end of tarso-metatarsus. 



The ecto- and endo-condylar fossae and the intercondylar ridge of the 

 R. tarso-metatarsus are still covered by articular cartilage, which, though 

 brown and dry with age, still presents distinctive characters. 



The ecto-condylar fossa is as broad as long, and is shallow ; the endo- 

 condylar fossa is longer than broad and is deep. 



The margins of these fossae are sharply defined and prominent with the 

 exception of the posterior border of the ecto-condylar fossa, which is rounded 

 from before backwards so as to adapt it for the shape, and to facilitate the 

 movements on it of a sesamoid bone.* (PL XIX., fig. 1, a.) 



The marginal prominence, and consequently the increased depth of the 

 fossse, is caused by a rim of fibro-cartilage (fig. 1, b) which is fused into the 

 margin of the true articular cartilage in all parts except one, viz., the outer 

 and posterior margin of the ecto-condylar fossa. 



This separation is natural, and the free part is semilunar in form (fig. 1, c), 

 bevelled from without inwards, and so contributing materially to increase the 

 depth of the fossa at the sides in a somewhat similar way to what the semi- 

 lunar cartilages act in the knee-joint of man. 



This free semilunar cartilage is continuous with the sharp cartilage skirting 

 the anteroinferior border of a sesamoid bone to be afterwards described. 



Calcaneo-sesamoid bone, fig. 1, a : — 



Its position has been before mentioned. Its general form is pyramidal, 

 having two ends, three surfaces, and three borders. 



* The difference between the two fossae at their posterior margin may be well s n 

 in a bone denuded of cartilage. The caleaneo-sesamoid bone is only connected with the 

 ecto-condylar fossa. Yet it is right I should mention a curious fact observed by Captain 

 Hutton when superintending the excavation of the Moa remains at Hamilton Swamp. 

 He observed a leg of the Moa (probably D. ekphantopus ? or D. crassus ?) with all the 

 bones loose but in situ, and he especially noticed in this case two sesamoid bones at the 

 tibio-tarsal joint. Bearing in mind the general positions and functions of sesamoid bones, 

 the morphology of the tibio-tarsal joint in other birds, also the marked inarticular 

 character of the posterior margin of the endo-condylar fossa in Dinornis, together 

 with the degree of prominence and strength of the endo-calcaneal process, I should 

 think it quite possible that the second sesamoid bone Captain Hutton saw in the 

 Hamilton Swamp specimen was from the opposite limb, and had fallen accidentally into 

 apposition with the other one. 



