90 ON PALLAS' CORMORANT STE.INEGER AND LUCAS. 



The number of ribs articulating with the sternum is, however, subject 

 to slight variation, especially among water birds, and without an ex- 

 tensive series of specimens it is a little difficult to be sure of the normal 

 number. 



The coracoid is of the same length as that of carbo, 10 mm longer than 

 in urile ; but, while the proximal end is but little heavier than in carbo, 

 the shaft aud especially the distal end are much more massive. 



The epicoracoid is prolonged upward into a sharper hook than in any 

 of the other species at hand, but this process is subject to considerable 

 variation with age or in various individuals. 



One humerus is a little longer than that of carbo, the other is of ex- 

 actly the same length; both are much stouter, especially in the proxi- 

 mal half. 



The humerus is practically non-pneumatic, the foramina being very 

 minute, while the pneumatic foramina of carbo, though not large, are 

 readily seen. 



The humerus of urile differs from that of dilophus precisely as that 

 of perspicillatus from carbo. 



The ulna is distinguishable from that of carbo only by its greater 

 weight, and the same may be said of the humerus of urile as compared 

 with that of dilophus. 



The fused metacarpals are slightly shorter and slightly stouter than 

 in carbo, and here again the same differences are observable between 

 the metacarpals of urile and dilophus. 



The "sacrum," as a whole, is as long as that of carbo, but its com- 

 ponent parts are more heavily built. 



It comprises six presacrals, two true sacrals, and nine post-sacrals, 

 aud the three "sacra" of perspicillatus agree with one another in these 

 particulars. 



Phalacrocorax carbo has six pre-sacrals, two true sacrals, and nine 

 or ten post-sacrals. P. urile has six, two, eight, and dilophus six, two, 

 nine. 



The hypapophyses of the anterior three vertebras have been broken 

 off, but although the compressed centra are larger than in carbo, the 

 hypapophyses seem to have been smaller. 



The six presacrals present few salient characters, but the dia. 

 pophyses of the fourth vertebras lie at right angles to the vertebral 

 column, while in the three other species the diapophyses of this verte- 

 bra are directed forward. 



The sacral and immediate post-sacral vertebras vary in the develop- 

 ment of their parapophyses in all four species under consideration. 



In all three specimens of perspiciUatus the two true sacrals bear no 

 parapophyses, while the two succeeding vertebra* have them extended 

 to, and ankylosed with, the ilium. 



The diapophyses and parapophyses of these vertebras are united by a 

 thin plate of bone, but that this is due to age is shown by the condition 

 obtaining in the other species. 



