NO. 3 COMPAKATIVE HISTOLOGY OF FEMUR FOOTE 47 



Underneath this band is a single lamina with long, well-developed lacunse 

 and straight canalieuli, parallel with neither surface of the bone, but occupying 

 an irregular position. 



Underneath the lamina is a wide central ring of lamellae with oval lacunae 

 and bushy canalieuli, interrupted by frequent Haversian canals of the (la) 

 differentiation. A narrow ring of internal circumferential lamellae surrounds 

 the medullary canal. Threefold division. 



Type I-II-III, la. 



EIGHT FEMUR OF BUFO LENTIGINOSUS COGNATUS. NO. 13 11, U. S. NAT. MUS. 



Pl. 3, Fig. 37. Syn. Tab. I 



Antero-posterior diameter of bone, 2 mm. ; lateral, 1.5 mm. 



Antero-posterior diameter of medullary canal, 1 mm. ; lateral, 0.9 mm. 



The medullary canal is full. Medullary index, 42%. 



Structure. — The three divisions are evident. The external circumferential 

 lamellae, with long lacunae and straight canalieuli, surround the section. The 

 central ring is composed of lamellae with oval lacuna perforated by Haversian 

 canals of the (la) differentiation. The internal circumferential lamellae form 

 a narrow ring around the medullary canal. 



Type I-III, la. 



RIGHT FEMUR OF BUFO VALLICEPS. NO. E 21 5, U. S. NAT. MUS. 



Pl. 3, Fig. 38. Syn. Tab. I 



Antero-posterior diameter of bone, 2 mm. ; lateral, 1.5 mm. 



Antero-posterior diameter of medullary canal, 0.9 mm. ; lateral, 0.8 mm. 



The medullary canal is full. Medullary index, 31%. 



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

 lacunae and bushy canalieuli. It is perforated by numerous Haversian canals of 

 the (la) differentiation. In the inner wall many radiating canals appear. The 

 canalieuli from adjacent lacunae extend into both the circular and radiating 

 canals. A narrow ring of internal circumferential lamellae encloses the medul- 

 lary canal. Twofold division. 



Type I-III, la. 



RIGHT FEMUR OF RANA BOYLII. NO. F 61 20, U. S. NAT. MUS. 



Pl. 3, Fig. 39. Syn. Tah. I 



Antero-posterior diameter of bone, 1 nnn. ; lateral, O.fi mm. 

 Antero-posterior diameter of medullary canal, 0.5 nun.; lateral, 0.4 mm. 

 The medullary canal is full. Medullary index, 47%. 



