64 SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE VOL. 35 



BIGHT FEMUR OF ARA MACAO. MACAW. CR. MED. COLL. 



Pl. 5, Fig. 84. Stn. Tab. Ill 



Antero-posterior diameter of bone, 5.5 mm. ; lateral, 4.5 mm. 



Antero-posterior diameter of medullary canal, 4.5 mm. ; lateral, 3.5 mm. 



The medullary canal is full. Medullary index, 178%. 



Structure. — The bone is composed of rather crude laminfe, separated and 

 crossed at various angles by numerous canals and interrupted here and there 

 by a few Haversian systems of the (Ic) diiferentiation. In the posterior ridge 

 the systems form a considerable portion of the thickness of the wall. The 

 laminae are composed of a few lamellae with oval and round lacunae and short, 

 bushy eanaliculi. 



Type II-III, Ic. 



RIGHT FEMUR OF NYCTHEKODIUS VIOLACEUS. NIGHT HERON. CR. MED. COLL. 



Pl. 5, Fig. 85. Syn. Tab. Ill 



Antero-posterior diameter of bone, 5 mm. ; lateral, 6 mm. 



Antero-posterior diameter of medullary canal, 4 mm.; lateral, 4.5 mm. 



The medullary canal is full. Medullary index, 148%. 



Structure. — The external circumferential lamellae are not distinct. The 

 bone is composed, for the most part, of short, irregular, and incomplete laminte, 

 marked off by short, concentric canals. The laminae are interrupted by small 

 Haversian systems of the (Ic) differentiation which form nearlj^ the whole of 

 the posterior ridge. Each lamina consists of a few lamellae with oval lacunae 

 and bushy eanaliculi. The canals separating the laminae are wide and short, and 

 not often uniting. Internal circumferential lamella^ with long lacunae and 

 straight eanaliculi surround the medullary canal. 



Type II-III, Ic. 



FEMUR OF PAVO CKISTATUS. PEAFOWL. CR. MED. COLL. 



Pl. 5, Fig. 86. Syn. Tab. Ill 



Antero-posterior diameter of bone, 10 mm.; lateral, 11 mm. 



Antero-posterior diameter of medullary canal, 8 mm.; lateral, 10 mm. 



The walls of the bone are thin. The medullary canal is large, empty, and 

 lias a network of trabeculae which extends from one wall in a downward direc- 

 tion to the opposite wall. 



Medullary index, 277%. 



Structure. — The section is composed of a concentric network of canals 

 enclosing short laminjc. The canals intersect at all angles. The laminae, com- 

 posed of bone substance with oval lacunae and relatively few rather short, 



