38 SMITHSONIAN CONTEIBUTIONS TO KNOWLEDGE VOL. 35 



EIGHT FEMUR OF AMBLYSTOMA TIGRINUM. AMER. MUS. NAT. HIS. 



Pl. 2, Fig. (i. Syn. Tab. I 



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



Aiitero-posterior diameter of medullary canal, cancellons meshes. 



Medullary index, 0. 



Structure. — The section has no distinct medullary canal. It is composed 

 of a narrow external ring of lione suhstance, with a few oval lacunae and bushy 

 canaliculi, from the under portion of which a cancellous center is derived. The 

 meshes are filled with structureless material, and their walls have the same 

 structure as the walls of the bone. 



Type I. 



RIGHT FEMUR OF HYLA VERSICOLOR. TREE FROG. AMER. MUS. NAT. HI.ST. 



Pl. 2, Fig. T. Syn. Tab. I 



Antero-posterior diameter of bone, 0.8 mm. ; lateral, 0.8 mm. 



Antero-posterior diameter of medullary canal, 0.2 mm.; lateral, 0.2 mm. 



The medullary canal is full. Medullary index, 7%. 



Structure. — The entire section is composed of lamellfe with round and oval 

 lacun.TP and bushy canaliculi enclosing the medullary canal. The section has 

 a uniform structure. 



Type I. 



RKiHT FEMUR OF HYLA ARENICOLOR. NO. E 50 30, U. S. NAT. MUS. 



Pl. 2. Fig. 8. Syn. Tab. I 



Antero-posterior diameter of bone, 0.5 mm.; lateral, 0.5 mm. 



Antero-posterior diameter of medullary canal, 0.2 mm.; lateral, 0.2 mm. 



Tlie medullary canal is full. ]\Iedullary index, 19%. 



Slnicfnre. — The section is composed of concentric lamelhr witli oval lacuiue 

 and long, straight canaliculi, divided into wide external and narrow internal 

 rings which surround its medullary canal, thus showing a twofold division. 



Type I. 



RIGHT FEMUR OF HYLA FEMOR.\LIS. NO. E 60 23, U. S. N.\T. MUS. 



Pl. 2, Fig. 9. Syn. Tab. I 



Antero-posterior diameter of bone, 0.5 muL; lateral, 0.4 mm. 



Antero-posterior diameter of medullary canal, 0.2 mm.; lateral, 0.2 mm. 



The medullary canal is full. INfedullary index, 24 '/t . 



Structure. — The section is composed of concentric lamelkt with oval lacun.T 

 and long canaliculi, divided into wide external and narrow internal rings which 

 surround the medullary canal, a twofold division. 



Type I. 



