120 SMITHSOXrAX CONTRIBUTIONS TO KNOWLEDGE VOL. 35 



Tlio iiiednllavy cnnal is full. Medullary index, 62%. 



Stnictiire. — Tiie seftion has three divisious. A wide riu^ of external cir- 

 cumferential lauielliv, 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 lacuna' are long and narrow and the canalicnli are straight. 



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

 Haversian systems with inter-Haversian lamella?. 



The interna! circumferential lamella^ foi-m a narrow ring around the medul- 

 lary canal. 



Type I-III, la, C. 



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



I'l. IT), F[(!. 240. Syn. Tab. YI 



Anteroposterior diameter of bone, 13 mm.; lateral, 12 mm. 



Antero-posteridv diaiiieter of medullary canal, 9.5 mm.; lateral, i) 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-Ha\ersian structure. At the ridges the systems break through 

 the external circumferential lamellje 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 

 lacuna^ in all parts are well developed. 



TjTje I-III, la, C. 



RIGHT FEMUR OF LASIOPYGA SP. AFRICAN MONKEY. 

 NO. 163283, I'. S. N.\T. MUS. 



Vh. lo, Fig. 2il. 8yx. 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 



