92 



SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE 



vol. 35 



LEFT FEMUR OF CAVIA CUTLERI. GUINEA PIG. AMER. MUS. NAT. HIST. 



Pl. 9, Fig. 171. Syn. Tab. V 



Antero-posterior diameter of bone, 6 mm. ; lateral, 4 mm. 

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

 The medullary canal is full. Medullary index, 100%. 



Structure. — The three divisions are plainly marked. The external circum- 

 ferential lamellae with long lacuna? and straight eanaliculi form a narrow ring 

 around the bone. The central ring consists of basic bone substance with round 

 and oval lacunas and bushy eanaliculi, interrupted by poorly developed Ha- 

 versian systems of the (la) differentiation and crossed by radiating canals. In 

 the posterior wall the ring consists of crude Haversian systems between which 

 is bone substance with oval lacunae and bushy eanaliculi. 



The internal circumferential lamella? form a narrow ring arouud the medul- 

 lary canal. The bone shows a threefold division. 



Type I-III, la. 



LEFT FEMUR OF SCALOPUS AQUATICUS. MOLE. AMER. MUS. NAT. HIST. 



Pl. 9, Fig. 172. Syn. Tab. V 



Antero-posterior diameter of bone, 1.5 mm. ; lateral, 1.5 mm. 

 Antero-posterior diameter of medullary canal, 1 mm. ; lateral, 1 mm. 

 The medullary canal is full. Medullary index, 80%. 



Structure. — The section is composed of lamellae with long and oval lacunae 

 and straight eanaliculi, partially separated into two equal, concentric rings by 

 concentric, branching canals and crossed at various angles by radiating canals. 

 In the posterior wall the lamellae are crude Haversian systems of the (lb) 

 differentiation. 



Type I-III, lb. 



RIGHT FEMUR OF SOREX. SHREW. AMER. MUS. NAT. HIST. 



Pl. 9, Fig. 173. Syn. Tab. V 



Antero-posterior diameter of bone, 3 mm. ; lateral, 3.3 mm. 

 Antero-posterior diameter of medullary canal, 1.2 mm.; lateral, 1.5 mm. 

 The medullary canal is full. Medullary index, 22%. 



Structure. — The section is composed of bone substance with oval lacunae 

 and bushy eanaliculi, frequently interrupted by primitive Haversian systems of 

 the (lb) differentiation and crossed by canals. In some places fragments of 

 external circumferential lamellae appear. In the posterior wall is a group of 

 oval lacunae with short, bushy eanaliculi. 



The bone shows but little differentiation of structure. It is uniformly of 

 an early differentiation. 



Type I-III, lb. 



