106 SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE VOL. 35 



RIGHT FEMUR OF AUCHENIA GLAMA. LLAMA. NO. 36363, AMER. MUS. NAT. HIST. 



Pl. 11. Fig. 207. Syn. Tab. V 



Antero-posterior diameter of bone, 25 mm. ; lateral, 25 mm. 



Antero-posterior diameter of me<hillary canal. 17 mm. ; lateral, 15 mm. 



The medullary canal is full. Medullary index. 69%. 



Structure. — The section is composed of short and long concentric laminae 

 with long lacuna? and straight caualieuli, separated and crossed by canals and 

 frequently interrupted by small Haversian systems of the (lb) differentiation. 

 The posterior ridge is composed of Haversian systems. Around the medullary 

 canal are many irregularly shaped spaces. 



Type II-III, lb. 



right femur of bangifer. reindeer. no. 4176, u. s. nat. mus. 

 Pl. 11, Fig. 208. Syn. Tab. Y 



Antero-posterior diameter of bone, 26 mm. ; lateral, 23 mm. 



Antero-posterior diameter of medullary canal, 16 mm.; lateral, 11 mm. 



The medullary canal is full. Medullary index, 60%. 



Structure. — Beginning on both sides of the posterior ridge and extending 

 around the section is a liorseshoe band of laminae with long lacunae and straight 

 canaliculi, frequently interrupted by small, crude Haversian systems of the 

 (la) ditferentiation. The band constitutes the whole width of the wall with 

 the exception of the narrow internal circumferential lamellae. The posterior 

 ridge is composed of Haversian systems — (lb differentiation). The medullary 

 canal is surrounded l)y a ring of lamellae. 



Type II-III, la, lb. 



LEFT FEMUR OF URSUS AMERICANUS. BLACK BEAR. CR. MED. COLL. 



Pl. 12, Fig. 209. Syn. Tab. V 



Antero-posterior diameter of bone, 31 mm. ; lateral, 29 mm. 



Antero-posterior diameter of medullary canal, 22 mm.; lateral, 21 nun. 



The medullary canal is full. Medullary index, 105%. 



Structure. — The bone is nearly round and has thin walls. The anterior 

 wall is thickest. The bone is composed of short and long laminae having a 

 general concentric arrangement, but presenting a variety of positions in the 

 different portions of the wall. In the anterior and outer wall they are short 

 and long, having the curvature of the bone, or present short angular curves and 

 run transversely. The laminae are quite uniform in width and are separated 

 by distinctly wide canals. The lacunae are long and the canaliculi are straight. 



