THE MUSCLES OF THE UPPER EXTREMITY. 85 



is represented by two distinct muscles, wliile in birds 

 it is invarialjly a single one. It is absent altogether 

 in the Apteryx. Here in the Eaven, it arises from 

 the neural spines of the first four dorsals, or at least 

 from the spines of the leading four vertebrae, that 

 possess completed ribs. This origin lies l)eneath that 

 of the latissimus dorsi and the trapezius muscles, 

 where they overlap it. The fibres pass backwards 

 and outwards to insert themselves upon the posterior 

 third of the mesial border of the scapula, commencing 

 anteriorly about where the trapezius leaves oft', the 

 overlapping of these two muscles, in all the specimens 

 I have examined, being at their origins only. 



On the upper side of the shoulder-joint we find in 

 the Raven two very slender muscular slips, passing 

 from the shoulder-girdle to the humerus. They both 

 act as levators of the brachium, and perhaps too, to 

 a certain extent, counteract each other in pulling the 

 humerus forwards and backwards. 



Rautenmuskel (rhomboid eus). Wiedemann, p. 82. 



,, ,, Meckel, System, p. 307. 



„ „ Schopss, p. 93. 



Selenka, p. 108, No. 33. 



„ „ De Man, p. 104. 



„ „ Watson, p. 77. 



„ „ Carlsson, p. 17. 



Rliomboideus major et minor. Tiedemann, §§ 243, 244. 

 Rhomboides pt. (rhomhoideus). Fiirbringer, Morph. Jahrh., v. 

 Rhomhoideus profundus. Fiirbringer, Monoqraphie. 

 Rliomboideus superior. Weldon, p. 641." (See Gadow in Bronn's 

 Klassen des Thier-Reichs, vi. Band, pp. 218, 219.) 



"Der Rh. profundus stellt eine secundare Differenzirung des 

 Serratus profundus dar, die bei manchen Vogeln (z. B. mehreren 

 Ratiten) noch keine voile Selbststandigkeit gewonuen, bei anderen 

 (z. B. Pici und Capitoniden) nocli weiter geliende Sonderungen und 

 Zerfallbildungen erkennen lasst " (Fiirbringer). 



