1880.] MR. W. A. FORBES ON LEPTOSOMA DISCOLOR. 471 



the same muscle in the Coraciidae. In no other birds amongst the 

 Anomalogonatse is this muscle present. In the Cuculidse this 

 muscle is present, but its terminal tendon is not T-shaped, the sternal 

 moiety being undeveloped. 



The arrangement of the termination of the tensor patagii brevis 

 is represented in the accompanying figure (tig. 2, p. 470). 



The main tendon (t.p.br.) runs on to the ulnar side of the arm, 

 and there becomes fused with the fascia covering the muscles. 

 Before doing so, however, it crosses the su])erficial tendon of origin 

 of the extensor tnetacdfpi radialis longior {e.m.r.), which springs 

 from the humeral tubercle, and becomes firmly blended with it. 



It likewise sends off, distally, a special slip of tendon which joins 

 the same tendon of that muscle more externally (wristward). This 

 is much the same arrangement as in the Coraciidae, as described and 

 figured by Prof. Garrod (P. Z. S. 1876, p. 511, pi. 49. fig. 1), except 

 that in those birds the tendon of tlie tensor pntagii brevis is split 

 into two quite separate halves ; if these were united together, an 

 arrangement would be arrived at practically identical with that of 

 Leptosoma. In the Cuculidee the condition of things is quite different, 

 as in them the " undivided tendon runs on to the ulnar superficial 

 fascia without any complication" (/. c. p. 512). 



Of the leg-muscles, the gluteus primus is present, though small, 

 only slightly overlapping the biceps, and with its fleshy part not 

 reaching the innominate, to which it is attached only by fascia. The 

 ambiens \s absent; the fe mo ro- caudal is very large, but lacks the 

 accessory head, as in all Anomalogonatse. Both the semitendinosus 

 and its accessory are well developed, &s'isi\ve semimembranosus. The 

 biceps cruris, as usual, passes through a tendinous loop. The ob- 

 turator externus is well developed, and the obturator iiiternus is of 

 a very elongated oval shape. The formula of Leptosoma is therefore 

 — . A . X . Y, exactly the same as that of the Coraciidae and the 

 greater number of Anomalogonatous birds. In the Cuculidse the 

 ambiens is always present and well developed, and the accessory 

 femora-caudal usually so', giving a formula of + . A . (b) . X . Y . 

 Leptosoma is therefore clearly not Cuculine. In the Cuculidse, too, 

 the obturator internvs is triangular in shape, as in the Gallinse and 

 their allies ; in Leptosoma, as already stated, as in Coracias, it is 

 oval. 



The anomalous arrangement of the toes in Leptosoma made me 

 very anxious to observe the disposition of its deep plantar tendons, 

 these, in all " zygodactyle " Anomalogonatous birds, being arranged 

 in a manner quite unique amongst birds and entirely different from 

 that which obtains in the even-toed Homalogonatous birds {i. e. the 

 Psittaci, Cuculidse, and Musophagidse)^. 



But in Leptosoma neither of these conditions occurs ; on the 

 contrary, the disposition of its plantar tendons is exactly that found 

 in many birds with feet of the ordinary structure. This condition is 



^ It is absent only in Cuculus, Chrysococcyx, and Cacomantis, [Garrod's 

 MSS.] 



^ Vide Garrod, P. Z. S. 1875, p. 345. 



