L20 



SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE 



vol. 35 



The medullary canal is full. Medullary index, 62%. 



Structure. — The section lias three divisions. A wide ring - of external cir- 

 cumferential lamella 1 , interrupted by Haversian systems of the (la) differen- 

 tiation, surrounds the bone. In the posterior wall it is interrupted by irregu- 

 larly shaped Haversian systems. Canals cross the ring at various intervals. 

 The lacunae are long and narrow and the canaliculi are straight. 



The centra] ring is very narrow and composed of a few well developed 

 Haversian systems with inter-Haversian lamellae. 



The internal circumferential lamellae form a narrow ring around the medul- 

 lary canal. 



Type I-III, la, C. 



RIGHT FEMUR OF FELIS CANADENSIS. CANADA LYNX. CR. MED. COLL. 



Pl. 15, Fig. 240. Syn. Tab. VI 



Antero-posterior diameter of bone, 13 mm.; lateral, 12 mm. 

 Antero-posterior diameter of medullary canal, 9.5 mm. ; lateral, 9 mm. 

 The medullary canal is full. Medullary index, 121%. 



Structure. — The usual three structural rings are distinct. The external 

 circumferential lamellae form a wide ring around the section excepting at the 

 ridges of the inner and posterior wall where they are deficient. They are inter- 

 rupted by small, crude Haversian systems of the (la) differentiation; while in 

 the posterior wall much better developed systems form an important part of 

 the whole lamellar ring. 



The central ring is composed of well developed Haversian systems with 

 very little inter-Haversian structure. At the ridges the systems break through 

 the external circumferential lamellae and form the external surface of the bone 

 at these points. 



The internal circumferential lamellae form a narrow ring around the medul- 

 lary canal excepting a small portion of the posterior and inner wall. The 

 lacunae in all parts are well developed. 



Type I-III, la, C. 



RIGHT FEMUR OF LASIOPYGA SP. AFRICAN MONKEY. 

 NO. 163283, U. S. NAT. MUS. 



Pl. 15, Fig. 241. Syn. Tab. VI 



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

 Antero-posterior diameter of medullary canal, 3 mm. ; lateral, 2.5 mm. 

 The medullary canal is full. Medullary index, 38%. 



Structure. — External circumferential lamellae of varying widths surround 

 the bone. In the anterior and inner wall they form two-thirds of the thickness 



