108 SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE VOL. 35 



In the inner lateral wall is another aggregation of the same type of Haversian 

 systems. 



Type II-III, Ih. 



EIGHT FEMUB OF MEXICAN BUREO. CR. MED. COLL. 



Pl. 12, Fig. 213. Syn. Tab. V 



Antero-posterior diameter of bone, 30 mm. ; lateral, 23 mm. 



Antero-posterior diameter of medullary canal, 15 mm. ; lateral, 11 mm. 



The medullary canal is full. Medullary index, 31%. 



Structure. — The section is composed of concentric lamina, separated and 

 crossed by canals, and interrupted by crude and fairly well developed Haversian 

 systems. Several laminae extend from the anterior to the posterior wall along 

 the medullary surface of the inner wall. The internal circumferential lamella? 

 with long lacunse and straight eanaliouli form a narrow boundary of the medul- 

 lary canal. Haversian systems occupy the mid-line of the posterior ridge. 



Type IT. 



RIGHT FEMUR OF TAPIRUS. TAPIE. NO. 35181, AMER. MUS. NAT. HIST. 



Pl. 12, Fig. 214. Syn. Tab. VI 



Antero-posterior diameter of bone, 32 mm. ; lateral, 35 mm. 



Antero-posterior diameter of medullary canal, 21 mm. ; lateral, 25 mm. 



The medullary canal is full. Medullary index, 98%. 



Structure. — The section is composed of laminae interrupted by two groups 

 of Haversian systems, one in the posterior outer ridge and the other in the 

 posterior inner ridge. In the anterior wall a few systems also appear. The 

 lacunas are oval, the canaliculi bushy, and cross canals are infrequent. A little 

 cancellous bone is seen in the anterior wall. The Haversian systems of the 

 posterior wall are separated by considerable inter-Haversian lamellae. 



Type II-III, C. 



LEFT FEMUR OF EQUUS HEMIONUS. WILD ASS OP ASIA. NO. 49493, U. S. NAT. MUS. 



Pl. 12, Fig. 215. Syn. Tab. VI 



Antero-posterior diameter of bone, 46 mm. ; lateral, 31 mm. 



Antero-posterior diameter of medullary canal, 26 mm.; lateral, 19 mm. 



The medullary canal is full. MeduUary index, 55%. 



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

 the entire thickness of the wall of the bone are laminae which are interrupted 

 by small Haversian systems, and also alternate with Haversian systems. The 

 systems are most numerous in the posterior wall. There is nearly an equal 

 concentric division of the laminae. In the external portion they follow a regular 



