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N EW YORK STATE MUSEUM 



With respect to the ribs, the last pair of haemapophyses do not 

 meet the costal border of the sternum upon either side. 



With respect to the pelvis, it is more transversely spread out, or 

 flattened in a vertical direction ; the gluteal ridges are not nearly 

 so prominent, and it is at once distinguished by hardly exhibiting 

 any flexion downward and forward of the postacetabular moiety. 



The sternum is shorter and at the same time broader. The an- 

 terior border of the keel often develops a small projecting spine; 

 the coracoidal grooves slightly decussate : the xiphoidal margin ex- 

 hibits but two very shallow emarginations, one upon either side of 

 the carina. 



Elanoides also shows some differences in its limbs as compared 

 with Circus. The pectoral limbs being very much alike, these dif- 

 ferences are chiefly confined to the pelvic extremity. 



In the femur of Elanoides the trochanter is relatively broader, 

 and more raised above the summit of the bone. In the tibiotarsus 

 the pro- and ectocnemial ridges are almost entirely suppressed. The 

 fibula is nearly complete, quite as much so as it is in Pandion, being 

 carried clear down to the external condyle, and fused with the tibio- 

 tarsus only a short distance above it. 



The tarso)netatarsus presents some very decided differences ; the 

 hypo tar sicU process is in one piece with one large perforation in the 

 vertical direction. The bone itself is much flattened in the antero- 

 posterior direction, and hardly shows any longitudinal grooving be- 

 hind. Passing to the pedal digits, we are to observe that the basal 

 joint of the second toe is very short, almost cubical, in Circus, while 

 in Elanoides it is more than half as long as the joint that follows 

 it next beyond in the same toe. 



Y\ nile there is but very little difference in the size of the trunk 

 skeletons of these birds there is a very conspicuous difference in 

 the lengths of the bones of the pelvic limb. 



MEASUREMENTS IX CENTIMETERS AND FRACTIONS ' ELANOIDES CIRCUS 



Length of skull 6.6 6.6 



Length of femur 4.6 7.2 



Length of tibiotarsus 6.3 10.6 



Length of tarsometatarsus 3.4 8-3 



My material for Elan us leucurus is somewhat meager, 

 consisting of a mutilated skull, sternum and shoulder girdle, and 

 some limb bones. This is much to be regretted as even these frag- 

 ments show characters of unusual interest. The skull is sufficiently 



