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SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE 



VOL. 35 



The internal circumferential lamellae surround the medullary canal. In the 

 outer wall the lamellae take the form of a crescent which occupies half of the 

 width of the wall. Near the anterior wall the lamellae of the crescent cross the 

 medullary canal as a narrow band. The crescent is interrupted by a few Ha- 

 versian systems. The lacunae are long and narrow. 



Type I-III, la, C. 



RIGHT FEMUR OF A FACHACAMAC INDIAN. NO. 15, U. S. NAT. MUS. 



Pl. 27, Fig. 360. Syn. Tab. IX 



Antero-posterior diameter of bone, 24 mm. ; lateral, 20 mm. 

 Antero-posterior diameter of medullary canal, 12 mm.; lateral, 9 mm. 

 Medullary index, 27%. 



Structure. — The section is surrounded, with the exception of the posterior 

 ridge, by a horseshoe of lamellae and Haversian systems of the (la) and (C) 

 differentiations. The shoe becomes narrowest at the junction of the anterior 

 and outer wall where it is displaced by a wide expansion of the internal lamellae. 



The central ring, irregular in width, is composed of Haversian systems and 

 inter-Haversian lamellae. 



The internal circumferential lamellae form a wide, irregular ring around 

 the medullary canal. 



In the outer wall it expands into a wide crescent composed of lamellae 

 indistinctly separated into laminae. 



The lacunae are oval. 



Type I-III, la, C. 



LEFT FEMUR OF AN ADOLESCENT PACHACAMAC INDIAN. NO. 7, U. S. NAT. MUS. 



Pl. 27, Fig. 361. Syn. Tab. IX 



Antero-posterior diameter of bone, 20.5 mm. ; lateral, 18.5 mm. 

 Antero-posterior diameter of medullary canal, 9 mm. ; lateral, 7 mm. 

 The bone is adolescent. Medullary index, 20%. 



Structure. — The section is surrounded by external circumferential lamellae, 

 which are very frequently interrupted by small, crude Haversian systems. In 

 the posterior ridge the lamellae are deficient. 



The central ring is wide and composed of irregularly shaped Haversian 

 systems, cross canals, and short inter-Haversian lamellae with oval lacunae. The 

 internal circumferential lamellae enclose the medullary canal. In the outer wall 

 they assume the form of a crescent and are crossed by frequent radiating canals. 



Type I III, C. 



