96 SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE VOL. 35 



kight femuk ok mvog.vle moschata. desman. cu. mkd. coll. 

 Pl. 9, Fig. 183. Syx. Tab. Y 



ilutero-postei-ior diameter of bone, .5 mm.; lateral, 6.5 mm. 



Aiitero-i)osterior diameter of medullary raual, 2.5 mm.; lateial, ::! mm. 



Me<liillary canal lias no contents. Medullary index, 30%. 



St met lire. — The inner wall of the bone is extended in the foini of a ridge, 

 wliich is composed of a network of laminae and canals rumiini;- transversely and 

 occupying the outer four-fifths of the ridge. Each lamina is composed of lamelhi) 

 with long or oval lacunse and long branching or bushy canaliculi. Tlie inner 

 one-fifth of the ridge wall is composed of a iietAvork of lamina- running from 

 the medullary canal to the outer network. The remainder of the bone (anterior, 

 outer, and posterior wall) is composed of a very irregular, wide internal ring 

 of lamellsi surrounding the medullary canal and having an outer wavy border, 

 in some places distinct and in other places fused with an external network of 

 lamina;. Many canals cross the lamellae on their way from the medullary canal 

 to the middle of the -wall. Within the lamellar ring are several round or ellip- 

 tical bodies composed of lamella running lengtliwise of the cross-section. These 

 bodies are such as would result from a transverse section of solid pillars. In 

 the outer wall of the bone lamella form tlic entire thickness. Here and there 

 occur a few incomplete Haversian systems consisting of a central canal and 

 radiating canaliculi. Twofold division. 



Type I-II-III, lb. 



FEMUB OF CVXOMYS LCDOVICIANrS. PRAIIUE DOG. Ci:. MED. COLL. 



Pl. t), Fig. 183. Six. Tab. V 



Antero-posterior diameter of bone, 4.5 mm.; lateral, 5 nun. 



Antero-posterior diameter of medullary canal, 2.5 mm.; lateral, 3 nnn. 



The medullary canal is cmpt\-. Medullary index, 50':; . 



Structure. — The section is composed of external circumferential lamella 

 forming an irregular ring wliich reaches its greatest width in the inner wall. 

 Tlie lacuna are long and narrow and tlic canaliculi arc long. 



The central ring is composed of incomplete Haversian systems of the (lb) 

 differentiation. Their lamella^ are indistinct, their lacntur are oval, and their 

 canaliculi are bushy. 



A very wide ring of internal circumfei-ciit iai laiiu'lla' surrounds the Tucdnl- 

 lary canal. The ring is widest in the anterior wall. Tlieir lacuna' are long and 

 naridw and their canaliculi are long. Xiiiiierous canals ])ass fi-oni the medid- 

 lary canal across the lanu'lla- into the interior of the hnnc. 



Type I-TTT. Tb. 



