OSTEOLOGY 167 



passes the popliteus. It is best defined in Teonoma for the 

 reason of the greater prominence of the bone at the in- 

 sertion of the semimembranosus anticus in that subgenus. 

 The actual insertion of the popUteus is along a shght ridge, 

 definable only in fully adult specimens, that occurs over this 

 portion of the shaft near its center. Immediately laterad, 

 near the proximal end, is the unmarked insertion of the 

 semimembranosus posticus. Upon the proximal portion of 

 the crest of the tibia, or cranio-lateral border, is inserted the 

 gracihs, and farther distad, the semitendinosus. From the 

 medial ridge arises the flexor digitorum longus. 



Upon the superficial fascia upon the cranio-lateral portion 

 of the lower leg for half the length of the tibia is inserted the 

 biceps femoris posticus, and immediately distad, the tenuis- 

 simus. The lateral tibial fossa is located upon the lateral 

 aspect of the bone. It is shallowest in Neotoma and slightly 

 deepest in Teonoma. From its proximal border and ad- 

 joining portion of the caudal border arises the tibialis 

 anticus. Farther distad the extensor hallucis arises upon the 

 fascia extending from this border. 



The posterior tibial fossa is situated upon the caudal 

 aspect of the bone. From a portion of the medial border of 

 this, along a well-defined crest, arises the tibialis posticus. 



Upon the caudo-lateral portion of the distal shaft is the 

 articular surface with which the fibia is fused, as described 

 for the latter bone. 



The distal end of the tibia has three articular processes, 

 for articulation with the foot. The medial surface of two of 

 these constitutes the internal malleolus, with a well-defined 

 groove for the passage of tendons, least well marked in 

 Neotoma and best in Teonoma. In common with the re- 

 mainder of the bone the distal extremity is somewhat the 

 lightest in the former and most robust in the latter subgenus. 



Fibula. The fibula, is situated slightly latero-caudad of 

 the tibia. It is but a trifle shorter than the latter bone, 



