138 



SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE 



VOL. 35 



The central ring is composed of Haversian systems, irregular in shape and 

 of the (C) differentiation, between which are groups of lamellae extending in 

 different directions. A wide ring of lamellae, separated into laminae, surrounds 

 the medullary canal. The lacunae are long and the canaliculi are straight. 



Type II-III, la, C. 



BIGHT FEMUR OF CANIS LATBANS. COYOTE. CB. MED. COLL. 



Pl. 19, Fig. 378. Syn. Tab. VII 



Antero-posterior diameter of bone, 12 mm. ; lateral, 11.5 mm. 

 Antero-posterior diameter of medullary canal, 8 mm. ; lateral, 7 mm. 

 The medullary canal is full. Medullary index, 68%. 



Structure. — The section is surrounded by external circumferential lamellae 

 excepting its posterior ridge and anterior wall. Beginning on the outer lateral 

 side of the posterior ridge the lamellae separate into laminae. As they pass 

 around the outer lateral to the anterior wall the laminae decrease in number 

 until they are reduced to a few lamellae. The lamellae then pass around the 

 inner wall as a narrow band. 



Their lacunae and canaliculi are well developed. Underneath the lamellae 

 and laminae is a wide ring of well developed Haversian systems, widest in the 

 posterior wall where they form nearly the whole thickness of the posterior 

 ridge. The systems frequently unite by cross canals and have long, narrow 

 lacunae. The medullary canal is enclosed by a ring of lamellae. In the lateral 

 wall the lamellae gradually thicken and separate into several laminae which 

 form half the thickness of the wall. They are well developed. 



Type II-III, C. 



BIGHT FEMUB OF CAPBA. GOAT. CB. MED. COLL. 



Pl. 19, Fig. 279. Syn. Tab. VII 



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

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

 The medullary canal is full. Medullary index, 50%. 



Structure. — The section is surrounded by a ring of laminae, divided into 

 short, long, and irregular segments by transverse canals and interrupted by 

 small Haversian systems of the (lb) differentiation. Underneath this is a wide 

 central ring of laminae arranged concentrically and obliquely and interrupted 

 frequently by Haversian systems of the (lb) and (C) differentiations. In the 

 anterior and posterior wall are two crescents of Haversian systems, and in 

 the outer portion of the posterior wall a group of Haversian systems. 



A narrow ring of lamellae surrounds the medullary canal. The lacunae are 

 generally oval and the canaliculi are straight. 



Type II-III, lb, C. 



