NO. 3 COMPARATIVE HISTOLOGY OF FEMUR FOOTE 43 



from them. The eanalieuli frecjiieutly unite and form a fine network. In some 

 parts of the section there are large radiating canals extending the whole width 

 of the walls of the bone. These canals communicate with adjacent lacunae by 

 fine caualiculi. The section as a whole has a bushy appearance. The large 

 radiating canals seem to be found only in the frogs of large size. 

 Type I. 



RIGHT FEMUR OF SPELERPES RUBER. RED SALAMANDER. AMER. MUS. XAT. HIST. 



1?L. 2, Fi(i. 25. Syx. Tab. I 



Antero-posterior diameter of bone, 1 mm.; lateral, 1.5 mm. 



Antero-posterior diameter of medullary canal, 0.3 nnn.; lateral, 0.2 mm. 



The medullary canal is full. Medullary index, 4yf . 



Sfnictiire. — The entire section is composed of lamella' with elongated 

 lacunas and bushy canaliculi enclosing the medullary canal. The bone has a 

 uniform structure. 



Type I. 



RIGHT FEMUR OF CRVPTOBRANCHUS ALLEGHENIENSIS. HELLBENDER. 

 AMER. MUS. NAT. HIST. 



Pl. 2. Fig. 26. Syx. Tab. I 



Antero-posterior diameter of bone, 2.5 mm.; lateral, 1.5 mm. 



Antero-posterior diameter of medullary canal, 0.5 mm.; lateral, 0.5 mm. 



The medullary canal is full. Medullary index, 79f. 



Structure. — With the exception of a few lamella? around the medullary 

 canal the entire section is composed of round and oval lacunsp with bushy cana- 

 liculi embedded in bone substance and arranged concentrically around the 

 medullary canal. The medullary canal is relatively small. A slight structural 

 differentiation appears in the lamellfe around the medullary canal. Twofold 

 division. 



Type I. 



RIGHT FEMUR OF NECTURUS MACULATUS. AMER. MUS. NAT. HIST. 



Pl. 2. Fig. 2r. Syx. Tab. I 



Antero-posterior diameter of bone, 2 mm. ; lateral, 1.5 mm. 



Antero-posterior diameter of medullary canal, 0.5 mm. ; lateral, 0.5 mm. 



The medullary canal is full. Medullary index, 9%. 



Structure. — Around the section are a few enclosing lamellae Avith rather 

 long lacuna?. Nearly the entire section is composed of large, oval, round, and 

 elongated lacuna? with bushy canaliculi arranged radially between enclosing 

 lamelte. The arrangement of the lacuna? is such as to give a radiating appear- 



