112 



SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE 



VOL. 35 



RIGHT FEMUR OF TATU NOVEMCINCTUS. ARMADILLO. NO. 357, AMER. MUS. NAT. HIST. 



Pl. 13, Fig. 223. Syn. Tab. VI 



Antero-posterior diameter of bone, 7.5 mm. ; lateral, 16 mm. 

 Antero-posterior diameter of medullary canal, 5 mm. ; lateral, 6 mm. 

 The medullary canal is full. Medullary index, 33%. 



Structure. — The section has a long lateral diameter by extension of its 

 outer wall. It is composed of lamella? with oval and round lacunae and bushy 

 canaliculi, crossed in all directions by canals and interrupted by a few un- 

 developed Haversian systems of the (lb) differentiation. The outer process 

 has central cancellous bone. 



Type I-m, lb. 



RIGHT FEMUR OF TAMANDUA TETRADACTYLA. ANT-EATER. NO. 14866, 



AMER. MUS. NAT. HIST. 



Pl. 13, Fig. 224. Syn. Tab. VI 



Antero-posterior diameter of bone, 7 mm. ; lateral, 12 mm. 

 Antero-posterior diameter of medullary canal, 3 mm. ; lateral, 4 mm. 

 The medullary canal is full. Medullary index, 17%. 



Structure. — The longest diameter of the bone is its lateral diameter. The 

 outer wall is projected outward into a prominent ridge. Beginning on both 

 sides of the mid-line of the inner wall and extending around the section is a 

 band of external circumferential lamellae, interrupted in the anterior wall by 

 concentrically arranged small, crude Haversian systems of the (la) differentia- 

 tion, and in the posterior wall by a few fairly well developed Haversian systems. 

 The band is widest in the anterior wall and narrowest in the outer wall. The 

 lacunae are oval and long and the canaliculi are bushy and straight. 



Under this band is a central ring of Haversian systems of the (lb) dif- 

 ferentiation, between wdiich is bone substance with oval and large lacunae and 

 bushy canaliculi. The ring nearly reaches the external surface at the mid-line 

 of the inner wall. The systems are united by cross canals. Internal circum- 

 ferential lamellae form a rather narrow ring around the medullary canal. In 

 the outer and inner wall it assumes a cancellous form. 



Type I-m, la, lb. 



LEFT FEMUR OF GORILLA. GORILLA. NO. 22832, AMER. MUS. NAT. HIST. 



Pl. 13, Fig. 225. Syn. Tab. VI 



Antero-posterior diameter of bone, 16.5 mm. ; lateral, 19.5 mm. 

 Antero-posterior diameter of medullary canal, 7.5 mm. ; lateral, 9 mm. 

 The medullary canal is full. Medullary index, 15%. 



