44 



SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE 



VOL. 35 



ance. Around the medullary canal are a few lamellae with long lacunae and long 

 and straight canaliculi. Threefold division. 

 Type I. 



EIGHT FEMUR OF SCAPHIOPUS HOLBROOKII. SPADEFOOT TOAD. AMER. MUS. NAT. HIST. 



Pl. 2. Fig. 28. Syn. Tab. I 



Antero-posterior diameter of bone, 1.5 mm.; lateral, 1 mm. 

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

 The medullary canal is full. Medullary index, 11%. 



Structure. — The section is composed of two divisions, one, external, com- 

 posed of concentric lamellae with round and oval lacunae and long, straight 

 canaliculi, and the other, internal, composed of circumferential lamellae witli 

 long, narrow lacunae and long, straight canaliculi. Twofold division. 



Type I. 



RIGHT FEMUR OF SCAPHIOPUS COUCHII. NO. F 50 20, U. S. NAT. MUS. 



Pl. 2. Fig. 29. Syn. Tab. I 



Antero-posterior diameter of bone, 1 mm. ; lateral, 1.5 mm. 

 Antero-posterior diameter of medullary canal, 0.5 mm.; lateral, 0.6 mm. 

 Medullary canal is full. Medullary index, 24%. 



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

 canaliculi, indistinctly divided into concentric rings which surround the medul- 

 lary canal. 



Type I. 



RIGHT FEMUR OF SCAPHIOPUS HAMMONDII. NO. F 20 6, U. S. NAT. MUS. 



Pl. 2. Fig. 30. Syn. Tab. I 



Antero-posterior diameter of bone, 1 mm. ; lateral, 0.8 mm. 

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

 The medullary canal is full. Medullary index, 33%. 



Structure. — The section is composed of concentric rings of lamellae sur- 

 rounding a central medullary canal. The lacuna; are oval and the canaliculi 

 are long. 



Type I. 



RIGHT FEMUR OF PIPA AMERICANA. SURINAM TOAD. AMER. MUS. NAT. HIST. 



Pl. 3. Fig. 31. Syn. Tab. I 



Antero-posterior diameter of bone, 3.5 mm. ; lateral, 5.5 mm. 

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

 The medullary cana] is full. Medullary index, 3%. 



