334 



NEW YORK STATE MUSEUM 



condition, taken in connection with the general form of the sternum 

 in Olor, reminds one, to some little extent, of that bone as it exists 

 in such a genus as Gavia. In the shoulder girdle both the os 

 jure ula and the coracoids are highly pneumatic, while the scapulae 

 do not appear to enjoy that condition. The foramina are at the 

 usual sites, and are of good size in the fourchette. This bone has 

 the general anserine character, but is especially modified at the 

 inferior, mesial clavicular arch in order to admit of the passage 

 of the tracheal loop to and from its harborage in the intracarinal 

 recess provided for it by the sternum. Instead of the clavicles 

 forming a continuous arc below, as in ducks and geese generally, 

 this modification in Olor consists in an abrupt bending backward 

 of the lower fourth of the bone, and a drawing of the clavicles 

 closer together. The part thus bent posteriorly, is shared equally 

 by either clavicle, and their thoroughly fused symphysial part still 

 retains a position in the median plane. This supplementary loop, 

 as it were, lies nearly in the horizontal plane, so that when the 

 os furcula is disassociated from the rest of the skeleton, the furcula 

 may be made to stand up, by resting on the lower margin of this 

 backward-bent loop. At the symphysis beneath, there is a con- 

 siderable concavity, with a corresponding convexity on the other 

 side, which latter is uniformly continuous with the general round- 

 ness of the posterior aspect of this furcula. 



The free clavicular heads above are drawn out into long points 

 as they are in the geese, but the supraclavicular processes are very 

 rudimentary. The mesial aspects of the clavicular limbs are smooth, 

 the surfaces being unbroken ; while externally, upon either limb, 

 the surface is divided, and this by a raised ridge that follows the 

 general curvature of the clavicle for some little distance down. 

 This ridge is formed by the anterior part of the clavicular arc being 

 considerably thicker than it is behind, where it is also smoother. 

 Superiorly, upon either limb, we find the large pneumatic foramina 

 in the recess formed by this ridge in the locality referred to. 

 Passing to the coracoid, it is seen to agree exactly in character 

 with the coracoid of Branta canadensis, being simply 

 proportionately stouter, and about a centimeter higher, measuring 

 from the topmost point of the summit, to the apical point of the 

 inferoexternal angle of the expanded sternal extremity. 



A scapula also has the same form it has in Branta, but the bone 

 is longer in Olor, and relatively, as well as actually, somewhat nar- 

 rower. When articulated in situ, the manner of the articulation 

 of these bones of the shoulder girdle agrees in the two genera. 



