74 SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE VOL. 35 



Structure. — The section has the three divisions; the external circumfer- 

 ential lainelliB form a narrow ring around the section and have long lacuna 

 and straight canaliculi. The central ring is composed of Haversian systems 

 of the (Ic) differentiation between which are canals and short fragTuents of 

 lamelliB with oval lacunse and bushy canaliculi. The internal circumferential 

 lamelljE fonn a distinct, narrow ring around the medullary canal. Tlieir lacunas 

 are long and canaliculi are straight. 



Type I-III, Ic. 



RIGHT FEMUR OF ANTHRACOCEROS MALABARICUS. HORN BILL. NO. 2887, 



AMER. MVa. NAT. HIST. 



Pl. 7, Fig. 109. Syn. Tab. Ill 



Antero-posterior diameter of bone, 6.5 mm. ; lateral. G mm. 



Antero-posterior diameter of medullary canal, 5.5 mm.; lateral, 5 mm. 



The medullary canal is empty. Medullary index, 240%. 



Structure. — The section has three divisions. The external circumferential 

 lamellae with long lacun.Te and straight canaliculi fonn a distinct, narrow ring 

 around the bone. The central ring is composed of lainellje with round and 

 oval lacuna, interrupted by many canals and Haversian systems of the (Ic) 

 stage. The internal circumferential lamella with long lacuna form a narrow 

 distinct ring around the medullary canal. 



Type I-III, Ic. 



FEMUK OF ASTUR ATRICAPILLUS. GOSHAWK. CR. MED. COLL. 



Pl. 7, Fig. 110. Syx. Tab. Ill 



Antero-posterior diameter of bone, 4 mm. ; lateral, 4.3 mm. 



Antero-posterior diameter of medullary canal, 3 mm.; lateral, 3.3 mm. 



The medullary canal is empty. Medullary index, 139%. 



Structure. — The section is surrounded by external circumferential lamella, 

 fairly well developed. Their lacuna are more frequently oval tliau long. The 

 canaliculi are bushy. 



In the inner lateral posterior wall is a slight ridge to which are attached 

 muscle ienilons penetrating the external lamella. Underneath the external 

 circumferential lamella is a thick ring of Haversian systems of the (Ic) stage of 

 development. Tlie ring is crossed at all angles by wide, irregular canals. 



The medullary canal is enclosed by internal circumferential lamella with 

 long lacuna and canaliculi. 



Type I-III, Ic. 



