MARYLAND GEOLOGICAL SURVEY 61 



SO well preserved, and so characteristic, especially the humerus, that 

 the affinities of the species they indicate can be determined with toler- 

 able certainty. The most marked feature of the humerus is the trans- 

 verse obliquity of its shaft and distal extremity. Both are much 

 compressed, and so turned that the common plane of their longer 

 diameters, instead of being nearly vertical, as in the brachium of most 

 birds, is here highly inclined inward and downward. Among the other 

 characters of importance may be mentioned, the unusually small size 

 of the ulnar condyle, the very deep, oval impression for the attachment 

 of the anterior brachial muscle, and the presence of an elongated, com- 

 pressed apophysis, extending outAvard and upward from the exterior 

 margin of the distal end, just in front of the radial condyle. 

 " This humerus has the followino- dimensions : 



mm. 



Length of portion preserved 49.0 



Vertical diameter of distal extremity 13.3 



Transverse diameter of radial condyle 8.6 



Transverse diameter of ulnar condyle 3.8 



Length of impression of anterior brachial muscle 5.6 



Breadth of impression of anterior brachial muscle 3.8 



Longer diameter of shaft where broken 7.4 



Shorter diameter of shaft where broken 5.0 



" A comparison of the present fossils with the corresponding parts 

 of recent birds readily shows that the nearest allies of this extinct 

 species must be sought in the Auk family, or among the Petrels; as it 

 is only in these groups of birds, that the peculiar obliquity of the 

 humerus, noticed above, exists. In the Alcidce, however, this oblique 

 compression is greater than in the present specimen. The latter has, 

 moreover, on its outer edge above the radial condyle, the long, pointed 

 projection, which is not seen in the Auks, although present in the 

 Petrels, Gulls, and some of the wading birds. The difference in size 

 between the ulnar and radial condyles, and the remarkably deep, oval 

 impression for the attachment of the anterior brachial muscle show 

 unmistakably that this humerus belongs to one of the Shearwaters, and 

 apparently should be placed in the genus Pufftmis, with which it cor- 



