NO. 3 COMPAKATIVE HISTOLOGY OF FEMUR FOOTE 121 



of the section and in the posterior and outer wall about one-fourth of the entire 

 thickness. They are frequently interrupted by crude Haversian systems of the 

 (la) differentiation and crossed at various angles by short canals. Their lacunar 

 and canaliculi are well developed. The central ring is composed of well de- 

 veloped Haversian systems and lamella? with systems of the (la) diiferentiation. 

 The ring is widest in the outer lateral wall. 



In the lamellar portion of the ring are one or two concentric rows of 

 small Haversian canals which gradually change into the more completely 

 developed Haversian systems of the outer wall. The internal circumferential 

 lamellfE surround the medullary canal excepting in the outer wall. The lamellar 

 and Haversian portions of the section are about equal. 



Type I-IIT, la, C. 



EIGHT FEMUR OF MIDAS EUFONIGER. SOUTH AMERICAN MOXKEV (uPPER AMAZONj. 



NO. 14.548, V. S. NAT. MUS. 



Pl. 15, Fig. 242. Syn. Tab. VI 



Antero-posterior diameter of bone, 4.5 mm.; lateral, 4 mm. 



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



The medullary canal is full. iModnllary index, 74%. 



Structure. — The three structural rings are distinctly marked. The external 

 circumferential lamella form a thick enclosing ring of one-third to one-half the 

 thickness of the wall of the bone. The lamelte of the inner wall are very fre- 

 (juently dotted with small, clear, round spaces which are not present in the 

 outer wall. The lacuiife are well developed. 



The central ring is composed of rather irregularly shaped but well de 

 veloped Haversian systems, separated by inter-Haversian lamelte. They are 

 frequently united by canals. Tlie internal circumferential lamelhc form a nar- 

 row ring around tJie medullary canal, excepting in the outer wall where they 

 are deficient. 



Type I-III, la, C. 



■ LEFT FEMUR OF LEMUR. NO. 84383, IT. S. NAT. MUS. 



Pl. 15, Fig. 243. Syn. Tab. VI 



Antero-posterior diameter of bone, 10 mm. ; lateral, 8.5 mm. 



Antero-posterior diameter of medullary canal, 5.5 mm. ; lateral, 4.5 mm. 



The medullary canal is full. Medullary index, 41%. 



Structure. — The section is surrounded by a lamellar ring which is widest 

 in the anterior and posterior wall. Tn the inner wall it is divided into laminae, 

 and frequently interrupted by canals and very crude Haversian systems of the 

 (la) differentiation. The lacuna^ are generally well developed. The central 



