NO. 3 COMPARATIVE HISTOLOGY OF FEMUK FOOTE 65 



bushy canaliculi, ai'e interrupted by a few Haversian systems of the (Ic) 

 differentiation. 



Type II-III, Ic. 



FEMUR OF HAIjI^TUS LEUCOCEPHALUS. EAGLE. CR. MED. COLL. 



Pl. 5, Fig. 87. Stn. Tab. Ill 



Antero-posterior diameter of the bone, 13 mm.; lateral, 14 mm. 



Antero-posterior diameter of the medullary canal, 11 mm. ; lateral, 11.5 mm. 



The medullary canal is empty. Medullary index, 227%. 



Structure. — External circvmaferential lamellae surround the bone, excepting 

 the posterior ridge where they are interrupted by tendon attachments. Their 

 lacunae are long, narrow, and concentrically arranged and their canaliculi are 

 rather short and branching. 



The central ring of bone is composed of concentric laminae, interrupted by 

 Haversian systems of the (Ic) differentiation. The canals which separate the 

 laminae are relatively wide and, on account of their frequent communications 

 with neighboring canals, they present the appearance of a coarse network. 



Internal circumferential lamellae surround the medullary canal. They are 

 fairly well developed and are frequently crossed by canals extending inward 

 from the medullary canal. Their lacunae are long and narrow and their cana- 

 liculi are long and branching. 



On the posterior surface are two ridges, one central and one on the pos- 

 terior inner lateral border. The bone at these points consist of Haversian 

 systems of the (Ic) stage, separated by frequent wide canals which pass to an 

 apex at the outer surface of the ridges. The external circumferential laminae 

 are absent at these points and tendon insertions, interspersed with many canals, 

 occupy the posterior ridges. 



Type II-III, Ic. 



LEFT FEMUR OF ARAMUS VOCIFEKUS. COUKLAN. ?fO. 2859, AMER. MUS. NAT. HIST. 



Pl. 5, Fig. 88. Syn.' Tab. Ill 



Antero-posterior diameter of bone, 6.5 mm. ; lateral, 6 mm. 



Antero-posterior diameter of medullary canal, 5.5 mm. ; lateral, 5 mm. 



The medullary canal is empty. Medullary index, 239%. 



Structure. — The section is composed of concentric laminae with oval lacunae 

 and bushy canaliculi. In the anterior and posterior walls a single Haversian 

 system of the (Ic) stage is seen. Around the medullary canal is a narrow ring 

 of lamellae with long lacunae and straight canaliculi. The bone shows very little 

 variation of structure. 



Type II. 



