122 



SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE 



vol. 35 



ring, of varying widths, is composed of fairly well developed Haversian sys- 

 tems, small, large, and irregular in shape, and frequently united by canals. 

 Their lacuna? are well developed. In the anterior wall the ring is divided into 

 two nearly equal parts by a narrow, crescent-shaped lamina, the horns of which 

 begin about the middle of the lateral walls. The internal circumferential la- 

 mella? surround the medullary canal. It is widest in the inner wall and well 

 developed. 



Type I-III, la, C. 



EIGHT FEMUR OF LEMUR CATTA. RING-TAILED LEMUR. U. S. NAT. MUS. 



Pl. 15, Fig. 244. Syn. Tab. VI 



Antero-posterior diameter of bone, 8.5 mm. ; lateral, 7 mm. 

 Antero-posterior diameter of medullary canal, 7 mm. ; lateral, 4.5 mm. 

 The medullary canal is full. Medullary index, 122%. 



Structure. — The section is surrounded by a heavy, dark ring of varying 

 widths composed of meshed bone work. The meshes are irregular in shape and 

 size. The ring is narrowest in the outer wall, widest in the inner and antero- 

 lateral, and of intermediate thickness in other situations. The meshes are 

 filled with dense material which adheres to the mesh walls even in extremely 

 thin places. The mesh walls are extensions of the external circumferential 

 lamellae. 



Underneath this ring is a wide lamellar ring, interrupted by cross and 

 longitudinal canals and crude Haversian systems of the (la) and (lb) differen- 

 tiations. In the posterior wall the ring is wide and coarsely lamellar and fre- 

 quently interrupted by large, irregular spaces. Underneath this is an irregu- 

 larly shaped ring of fairly well developed Haversian systems with numerous 

 spaces. The internal circumferential lamella? surround the medullary canal. 

 It is widest in the anterior and lateral walls. 



Type I-III, la, lb, C. 



LEFT FEMUR OF ATELES. SPIDER-MONKEY. ( TEHUANTEPEC. ) NO. 11842, 



U. S. NAT. MUS. 



Pl. 15, Fig. 245. Syn. Tab. VI 



Antero-posterior diameter of bone, 12.5 mm. ; lateral, 10.5 mm. 

 Antero-posterior diameter of medullary canal, 7 mm.; lateral, 5.5 mm. 

 The medullary canal is full. Medullary index, 42%. 



Structure. — The external circumferential lamellae form a wide ring sur- 

 rounding the section, excepting a small portion of the inner wall. The lamella? 

 are frequently interrupted by Haversian canals of the (la) differentiation and 

 small Haversian systems. The ring is widest in the posterior wall. The cen- 



