176 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. 



EIGHT FBMUK OF A PACHACAMAC INDIAN. NO. 15, V. 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, witli 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 lamelte 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 laminir. 



The lacunte are oval. 



Type I-III, la, C. 



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



Pl. 27, Fig. oGI. 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%. 



St nut tire. — Tlie section is surrounded by external circumferential lamellae, 

 wliicli are \ery t'requentl\ iiilci riiptcd by siuidl, cni<lf Haversian systems. In 

 the ))osteri()r rid^c the lamella' are deticient. 



The central riiii; is wide ami composed (if IiTegularly shaped Haversian 

 systems, cross canals, anti short inler-Haversian lamelhp witii oval lac-nna'. The 

 intenial circumferential lamella' enclose the metlullary canal. In the outer wall 

 they assume the form of a (^-escent and are crossed by frequent radiating canals. 



Type I III, C. 



