BIRD OR REPTILE WHICH? 723 



the bones either continue throughout life with their component parts 

 unsolidified together, or else indicate by clear marks their lines of union, 

 so that it is always easy to tell the number and configuration of which 

 each is composed. 



Thus far the characters which separate a reptile from a bird stand 

 so widely apart the interval between the highest living crocodile and 

 the nearest living bird (represented by such forms as the New Zealand 

 kiwis, the mooruk of Australia, the cassowary of the Moluccas, and the 

 rheas or ostriches of South America) is of such enormous magnitude 

 that it would seem needless to entertain any fear of mistaking a mem- 

 ber of the former group for one of the latter. Meanwhile let us with- 

 hold any decided opinion. 



On November 29, 1871, a letter to Prof. Dana, dated from San 

 Francisco, written by Prof. O. C. Marsh, of Yale College, New Haven, 

 Connecticut, announced the discovery of a portion of a large headless 

 skeleton in the upper chalk formation of Western Kansas, consisting of 

 the nearly entire posterior limbs, portions of the haunch-bones, several 

 segments from the neck and tail of the spinal column, and numerous ribs 

 all in excellent preservation. The long leg-bone exhibited on the front 

 aspect of its upper extremity the large crest which, as we have already 

 pointed out, is a remarkably Avian character ; along its shaft lay a 

 fibula developed as among the diving birds of the present day, to whose 

 thigh-bone also that of the fossil bore considerable resemblance. The 

 "hock-bone," in presenting a trifid pulley-shaped lower end, was bird- 

 like ; while in the oblique arrangement of these divisions it again 

 claimed affinities with the divers, whose toes are articulated in this 

 manner to facilitate the forward stroke of their feet through the water, 

 The external division, however, which projects beyond the other two, 

 and is twice the size of either, is developed in a way unknown in any 

 recent or fossil bird, and the bones of the toe supported by it are pecul- 

 iarly articulated to produce rigidity and prevent flexion, except in one 

 direction, in order by the interlocking of the bones to increase the 

 strength of the joints during the act of swimming ; for the whole limb 

 is unquestionably adapted for rapid motion through water. The haunch- 

 bone presents some resemblance to what is seen among the reptiles, 

 in the permanence as separate bones of some of the portions of which 

 it is composed, and in its not being firmly joined to the spine by bony 

 union as in ordinary birds. 



The examination so far of these interesting remains proved that the 

 skeleton was certainly a bird's. On comparing its various bones with 

 the corresponding ones in existing representatives, its affinities, notwith- 

 standing considerable divergences from all known recent or ancient 

 species and genera, were evidently with the swimming-birds, of which 

 it is the largest knowm exponent, and of these it most resembled the 

 great northern diver, near which, for a time, it received a niche with 

 the appellation of Royal Bird-of-the-Dawn {HesperorniB regalis). 



