1901.] ANATOMY 0¥ GKUIFORJ1 BIBDS. 639 



The superficial muscle shows a marked tendency to increase in 

 its anterior region and to decrease in its posterior region. In Otis, 

 a diastataxic form, it is extremely long, arising from eight or nine 

 vertebra?, and covering the deep muscle completely. In Eurypyga, 

 a diastataxic form, it is thick in front, but thins out posteriorly ; 

 in Phinochetus, a eutaxic form, it is almost separated into a thick 

 proximal and a thin distal portion. In the others, eutaxic or 

 diastataxic, except the G-ruinae, its proximal portion extends 

 beyond the deep muscle, and it thins out and disappears some 

 distance in front of the posterior end of the scapula, this condition 

 being best marked in the eutaxic Psophia, where it takes origin 

 only from three to four vertebra?. As an exception to the general 

 trend of modification within the group, the Gruina? present the 

 peculiar feature that it is the distal portion of the superior muscle 

 which is best developed ; this completely conceals the shorter 

 portion of the deep muscle, while that again extends further 

 forwards than the superficial muscle anteriorly and is left exposed. 



The conditions of the deep muscle, except in Gruinae, are less 

 irregular. In all the others it begins at the distal extremity of 

 the scapula and reaches forwards along the scapula to a less 

 extent in the diastataxic forms and in ffeliomis, and to a much 

 greater extent in the eutaxic forms, especially in Psophia and 

 Dicholop7iu6\ where it is extremely long, extending practically the 

 whole length of the scapula and a portion of the clavicle. The 

 deep muscle is certainly phylogenetically newer than the super- 

 ficial muscle (Tiirbringer) and is in process of growing forwards 

 along the scapula. There is a coincidence between this apocentricity 

 and eutaxy ; the apocentricity is least in the diastataxic Eurypyga, 

 greatest in the eutaxic PsopJiia and Dicholophidce. 



Biceps hrachialis. — In the Gruiformes, with the exception of 

 Rhinochetus, the biceps muscle of the arm does not present 

 variations of importance. Its chief origin is from the acrocoracoid, 

 but it has the usual secondary origin from the humerus, the latter 

 being weaker. It runs undivided in most of the members of the 

 group until close to its insertion, by tendons of nearly equal 

 thickness, to the opposite sides of the radius and ulna. In some of 

 the Rallida? the radial portion shows signs of doubling. In Shino- 

 rh, tus, as has been described by Beddard (1), there is a curious acces- 

 sory biceps ( text-fig. 76, B.a.) : Beddard described it as arising from 

 the humerus immediately below the insertion of the deltoid muscle ; 

 I found a much more extensive origin beginning on the scapula, 

 close to the insertion of the subscapularis internus and thence 

 parsing down the humerus, receiving fibres from Beddard's point 

 of origin. It is inserted to the radius close to the insertion of the 

 radial fork of the biceps. Cases are known in which the normal 

 biceps is divided, the radial tendon coming from the humeral or 

 coraco-b amend portion of the muscle, Scopus even having a double 

 origin and insertion to the radius and ulna; and a tendency to the 

 doubling of the coraoo-humera] portion appears in some Ballidee. 

 It seems most probable 'hat this accessory biceps in Ehinochetua is 



12 



