NO. 3 COMPARATIVE HISTOLOGY OF FEMUR FOOTE 89 



RIGHT FEMUR OF PTEROPUS. (jAVA.) NO. 12616, U. S. NAT. MUS. 



Pl. 8, Fig. 164. Syn. Tab. IV 



Antero-posterior diameter of bone, 3 mm. ; lateral, 3.5 mm. 

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

 The medullary canal is full. Medullary index, 91%. 



Structure.— The section is composed of concentric lamellae with oval and 

 long lacuna? and straight canaliculi, interrupted by many very crude Haversian 

 systems of the (la) differentiation. 



Type I-III, la. 



RIGHT FEMUR OF PTEROPUS LEPICOS. NO. 112404, U. S. NAT. MUS. 



Pl. 8, Pig. 165. Syn. Tab. IV 



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 concentric lamellae with oval and 

 long lacuna? and straight canaliculi crossed by numerous radiating canals. Here 

 and there a few very crude Haversian systems of the (la) differentiation are 

 seen. The bone is uniform. 



Type I-III, la. 



RIGHT FEMUR OF PTEROPUS. (TONGATABU.) NO. 173884, U. S. NAT. MUS. 



Pl. 8, Fig. 166. Syn. Tab. IV 



Antero-posterior diameter of bone, 3 mm. ; lateral, 3 mm. 

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

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



Structure. — The section is composed of concentric lamellae with oval lacuna? 

 and straight canaliculi, partially separated by undeveloped Haversian systems 

 of the (la) differentiation into two laminae. The systems occupy a central 

 concentric position. The bone has a twofold division. 



Type I-III, la. 



RIGHT FEMUR OF PTEROPUS POLIOCEPHALUS. U. S. NAT. MUS. 



Pl. 9, Fig. 167. Syn. Tab. IV 



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

 Antero-posterior diameter of medullary canal, 2 mm. ; lateral, 2 mm. 

 The medullary canal is full. Medullary index, 49%. 



Structure. — The section has the three concentric divisions, external, central, 

 and internal. The lacuna? are oval and the canaliculi are straight. In the cen- 



