668 DR. p. CHALMERS MITCHELL ON THE 



I have no standard for comparison in the case of the caudal 

 muscles. The chief difference from the condition in Leptoptilus 

 is the absence of the inner slip of the ilio-coccygeus. 



Muscles of the Shoulder and Wing. 



Cucullaris. — The cervical portion is well developed, forming a 

 definite sheet of circular fibres which stop abruptly in line with 

 the proximal edge of the rhomboideus externus where they are 

 inserted along the clavicle. 



Rhomhoideus extermos. — Origin tendinous from the neural 

 crests of five and a lialf vertebrae beginning at just opposite the 

 junction of the scapula and clavicle. The fibres run outwards 

 nearly transversely to all the scapula except the down-turned 

 posterior end and forwards to part of the clavicle (text-fig. 125, 

 P.h. 2). 



Jihomboideus profundus or internus. — Origin tendinous, a little 

 short of the externus proximally and reaching just beyond it 

 distally. The fibres run outwards and backwards to no part of 

 the clavicle but to the whole length of the scapula including the 

 down-tui-ned end (text-fig. 125, Rh. 1). 



The two rhomboid muscles are nearly equal in thickness. 

 These tAvo muscles, according to Fiirbringer, and my own obser- 

 vations confii'm his view, are in pi'ocess of creeping forwards. 

 Their condition in Balceniceps shows a considerable degree of 

 specialization, but I have not material to compare the condition 

 in allied birds. 



Latissimus dorsi anterior. — A broad strap of muscle arising 

 from the anterior dorsal vertebrte only and I'unning downwaids 

 and forwai-ds, dipping under the anconseus, to a fleshy insertion to 

 the shaft of the humerus distal of the insertion of the posterior 

 division of the muscle and unconnected with it (text-fig. 125, L.A.). 



Latissimus dorsi 2)osterior. — Fleshy oi-igin, the anterior edge of 

 which touches but is not fused with the posterior edge of the 

 anterior division. Origin wider than that of the anterior 

 division, but not reaching quite as far back as the proximal edge 

 of the ilium. Its fibres converge to form a band about the same 

 width as the lat. dorsi anterior (text-fig. 125, L.P. 1), pass under 

 that muscle with a more proximal slope, to be inserted along a 

 strong tendon (text-fig. 125, L.P. 2) which is inserted to the 

 scapula under the scapular anchor of the ancoupeus, proximal to 

 the insertion of the lat. dorsi anterior, and which joins the 

 anconasus belly distally. 



Latissimus dorsi metapatag talis. — Absent. 



The anterior division is like that in Leptoptilns. The connec- 

 tion of the tendon of insertion of the posterior division with the 

 a,nconfeus occurs also in Leptoptilus, but I have noted a somewhat 

 similar arrangement in Bubo maxim.us. The loss of the meta- 

 patagial division has been noted by Fiirbringer in Plotus, but it 

 is usually present in the Herons, Storks, and Steganopods. 



