4(3 SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE VOL. 35 



Haversiaii canals of the (la) differentiatiou. luteriial circumferential lamellae 

 form a narrow ring around the medullary canal. 

 Type I-III, la. 



RIGHT FEMUE OF BUFO COLUMBIENSIS. NO. E 40, U. S. NAT. MUS. 



Pl. 3, Fig. 34. Syn. Tab. I 



Antero-posterior diameter of bone, 2 mm. ; lateral, 2 mm. 



Antero-posterior diameter of medullary canal, 1.4 mm.; lateral, 1.3 mm. 



The medullary canal is full. Medullary index, 111%. 



Structure. — The section shows the three divisions, external circumferential 

 lamellae very thin, central ring of lamellae, and internal circumferential lamellae. 

 The external lamellae are little more than a condensation of the external portion 

 of the central ring. The central ring consists of concentric lamella; with oval 

 lacunae. In the posterior and part of the lateral walls, oval lacunae with bushy 

 eanaliculi are crowded together between the central ring and internal lamellae. 

 A few canals appear in the inner wall. The internal circumferential lamella:! 

 form a narrow ring around the medullary canal. 



Type I-III, la. 



RIGHT FEMUR OF BUFO LENTIGINOSUS WOODHOUSII. NO. E 45 9, U. S. NAT. MUS. 



Pl. 3, Fig. 35. Syn. Tab. I 



Antero-posterior diameter of bone, 2.5 mm. ; lateral, 2 mm. 



Antero-posterior diameter of medullary canal, 1.5 nnn.; lateral, 1 mm. 



The medullary canal is full. Medullary index, 45%. 



Structure. — The section is composed of a thick ring of concentric lamellae 

 with oval lacunas, crossed by numerous radiating canals and perforated by a 

 few Haversian canals (la). Internal circumferential lamellae form a narrow 

 ring around the medullary canal. Twofold division. 



Type I-III, la. 



RIGHT FEMUR OF BUFO AMERICANUS. AMERICAN TOAD. AMER. MUS. NAT. HIST. 



Pl. 3, FiG. 36. Syn. Tab. 1 



Antero-posterior diameter of bone, 2.5 mm. ; lateral, 2 mm. 



Antero-posterior diameter of medullary canal, 1 nuiL ; hitcral, (t.n mm. 



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



Structure. — The section is surrounded by a wide band of lamella; with oval 

 lacuna; and bushy eanaliculi, interrupted by frequent Haversian canals of the 

 (la) differentiation. The band is widest in the anterior and inner walls. 



