128 SMITHSONIAN CONTKIBUTIONS TO KNOWLEDGE VOL. 35 



EIGHT FEMUR OF BISON AMERICANUS. BISON. NO. 22914, AMER. MUS. NAT. HIST. 



Pl. 16, Fig. 255. Syn. Tab. VI 



Antero-posterior diameter of bone, 56 mm. ; lateral, 46 mm. 



Antero-posterior diameter of medullary canal, 39 mm. ; lateral, 33 mm. 



The medullary canal is full. Medullary index, 100%. 



Structure. — The bone is chiefly composed of laminae. There are two aggre- 

 gations of Haversian systems, one in the posterior ridge and the other in the 

 angle of the inner wall. They are fairly well developed and occupy nearly the 

 whole thickness of the wall. Their lacunae are oval. The remainder of the 

 section is composed of laminae, interrupted by small Haversian systems. The 

 lacunae are oval and the canaliculi are straight. 



Type II-III, C. 



RIGHT FEMUR OF A MULE. NO. 227, CR. MED. COLL. 



Pl. 16, Fig. 256. Syn. Tab. VI 



Antero-posterior diameter of bone, 60 mm. ; lateral, 55 mm. 



Antero-posterior diameter of medullary canal, 47 mm. ; lateral, 45 mm. 



The medullary canal is full. Medullary index, 179%. 



Structure. — The section shows a posterior and outer ridge. The posterior 

 ridge is composed of small Haversian systems and inter-Haversian lamellai 

 witli oval lacunae and bushy canaliculi. Many spaces occur and the laminae 

 are crossed by numerous short canals. The outer ridge consists of Haversian 

 systems and laminae and shows a large number of spaces. Between these two 

 ridges the wall is composed of Haversian systems and laminae. The remainder 

 of the section is composed of laminte, interrupted by Haversian systems and 

 crossed by canals. Half of the anterior and inner walls is composed of laminae 

 perforated with spaces. The spaces have no walls but those of adjoining la- 

 minaj. They appear to be the result of senile clianges. Tlie bone is tliiu and 

 fragile. 



Type II-III, C, senile. 



LEFT FEMUR OF A MULE. NO. 229, CE. MED. COLL. 



Pl. 16, Fig. 267. Syn. Tab. VI 



Antero-posterior diameter of bono, 68 mm. ; lateral, 50 mm. 



Antero-posterior diameter of iiicdullary canal, 40 iiiiii.; latci-al, ,'57 iiiiii. 



The medullary canal is full. Mednlhiry index, 77%. 



Structure. — The section has three ridges, a posterior ridge and one on 

 either side of the anterior wall. The jjosterior ridge is composed of short 

 lamellae with branching canals, having a direction toward the point of the ridge. 



