NO. 3 COMPARATIVE HISTOLOGY OF FEMUR FOOTE 123 



tral ring is composed of well developed Haversiau systems witli some inter- 

 Haversian lamellfe. The systems displace the external circnmferential lamella? 

 in the anterior portion of the inner wall where they fonn the external boundary 

 of the bone. 



The internal circumferential lamellfe surround the medullary canal. They 

 are most prominent in the imiov wall. The lacuna? of the three rings are well 

 developed. 



Type I-III, la, C. 



RIGHT FEMUR OF CALLICEBUS TOBQUATUS. SQUIRREL-MONKEY. NO. 105539, 



U. S. NAT. MUS. 



Pl. ]5, Fig. 346. Syn. Tab. VI 



Antero-posterior diameter of bone, 5.5 mm. ; lateral, 5 mm. 



Antero-posterior diameter of medullary canal, 4 mm.; lateral, 3.5 mm. 



The medullary canal is full. Medullary index, 104%. 



Structure. — The anterior and outer half of the section is surrounded by a 

 wide band of external circumferential lamellse, interrupted by Haversian canals 

 of the (la) dift'erentiation, underneath which is a narrow half ring of Haversian 

 systems bordering upon the medullary canal. The lacuna^ of the lamellae and 

 Haversian systems are oval and long and the canalieuli are generally long and 

 straight. 



The posterior and inner half of the section is composed of irregularly 

 shaped Haversian systems fonning the whole thickness of the posterior and 

 inner wall. The external and internal circumferential lamellse are not distinct 

 from the remaining structure. 



Type I-III, la, C. 



LEFT FEMUR OF GENETTA. GENET. NO. 163294, U. S. NAT. MUS. 



Pl. 15, Fig. 247. Syn. Tab. VI 



' Antero-posterior diameter of bone, 9 mm.; lateral, 7 nun. 



Antero-posterior diameter of medullary canal, 6.5 mm.; lateral, 5 mm. 



The medullary canal is full. Medullary index, 107%. 



Structure. — A ring of external circumferential laiuella' of varying widths 

 surrounds the section. Tn the anterior wall it forms nearly the whole thickness; 

 it then becomes narrow in the outer wall, remains about the same width in the 

 posterior wall, and again widens in the inner anterior wall. It is interi'upted 

 by crude Haversian systems of the (la) differentiation in the anterior, inner, 

 and posterior wall. The lacunae are oval and long, and the canalieuli are long 

 and straight. Underneath the lamellar ring is an irregular ring of Haversian 

 systems well developed. The ring is widest in the lateral and posterior wall. 

 The systems are irregular in shape in the outer wall. Their lacuna* are oval 



