46 



SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE 



VOL. 35 



Haversian canals of the (la) differentiation. Internal circumferential lamellae 

 form a narrow ring around the medullary canal. 

 Type I-III, la. 



RIGHT FEMUR 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, 1.5 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 lamellae with oval 

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

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

 A few canals appear in the inner wall. The internal circumferential lamellae 

 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. \ 



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

 Antero-posterior diameter of medullary canal, 1.5 mm. ; 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 lacunae, 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. 3(5. Syn. Tab. I 



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

 Antero-posterior diameter of medullary canal, 1 mm. ; lateral, 0.6 mm. 

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



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

 lacuna 1 and bushy canaliculi, interrupted by frequent Haversian canals of the 

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



