502 STRUCTURE AND CLASSIFICATION OF BIRDS 



The ostrich 1 has the complete leg muscle formula 

 ABXY+. 



The femorocaudal is fleshy, but not large, and has no 

 distinct tendon of its own. It blends above with the acces- 

 sory. The accessory femorocaudal is an enormous muscle 

 ending in a broad thin tendon which distally is lost in a 

 fibrous expansion round the great vessels and nerves of the 

 thigh. The accessory semitendinosus is small. The tendons 

 of the semimembranosus and the semitendinosus become 

 united just after the attachment to the latter of the acces- 

 sory; they soon, however, diverge, the semimembranosus 

 being continued as a long thin tendon down the leg to join 

 the tendon of the gastrocnemius. The obturator externus 

 and the adductors are small ; the obturator internus is very 

 large. The ambiens does not arise from the pectineal pro- 

 cess, or even from the pubis, but from the ilium^ An 

 additional adductor muscle which has been referred to in 

 the cassowary also exists in the ostrich ; it has, however, 

 but one (tendinous) head, arising from the femorocaudal 

 piuscle. 



The rhomboideus superficialis of Bhea ^ springs, like that 

 of Struthio, from the spinous processes of the cervical verte- 

 brae, but from a larger number (four). It is inserted on to 

 the coracoid as well as the scapula. The rhomboideus pro- 

 fundus arises from the spinous processes of the first three 

 dorsals. As in carinate birds the serratus superficialis is 

 composed of an anterior and a posterior section ; the former 

 arises as a single band from the last cervical rib, and is 

 attached to the front part of the scapula ; the latter is large 

 and consists of three broad slips springing from the first 

 three dorsal ribs and their uncinate processes ; it is attached 

 to the hinder end of the scapula. It may be, Fuebeingbe 

 thinks, that a portion of this is really the pars superficialis 



' S. Haughton, ' On the Muscular Mechanism of the Leg of the Ostrich,' 

 P. R. Irish Ac. ix. (1866), p. 50 ; A. Macalistee, ' On the Anatomy of the 

 Ostrich,' ibid. 1867, p. 1 ; Ai.ix, ' Sur I'Appareil Locom. de I'Autruche de 

 I'Afrique,' Bull. Soc. Philem. 1868. 



^ S. Hauohton, ' Muscular Anatomy of the Rhea,' P. R. Irish Ac. ix. (1867) , 

 p. 497. 



