172 COUES ON THE OSTEOLOGY OF COLYMBUS TORQUATUS. 



pass through the canals of the bony protuberance which is superimposed upon the base of 

 the metatarsal bone, and proceed to their different digital insertions. This bony canal is 

 subdivided by osseo-cartilaginous septa into three divisions : a quite large central posterior 

 one, through which the majority of the tendons pass ; and two or three smaller latero- 

 anterior ones, for special tendons. I will notice two of these muscles which are quite 

 distinct as to their insertions, and consider the others collectively as the digital flexors. 



Tibialis posticus ? A muscle which I thus doubtfully homologize, not from its position, 

 but from its insertion and evident action, arises from the very apex of the tibial spine, and 

 from the fibrous septa between it and contiguous muscles. Its tendon passes with the 

 others through the fibro-cartilaginous envelope ; but then divaricates, to be inserted into 

 the inner aspect of the base of the metatarsal bone. It is the evident antagonist of the 

 peroneus already described ; directing and limiting the rotation of the tarsus. 



The inner anterior toe has a special flexor of considerable size. Its tendon passes over 

 the back of the joint, through one of the smaller divisions of the bony canal ; and proceeds 

 to its insertion along a deep groove on the posterior edge of the metatarsal bone. 



The common flexors of the digits as usual consist essentially of two sets, a perforans and per- 

 foratus, though the expressions " superficial " and " profound " do not here hold good, as 

 they have no such relative position. The tendons of the two sets, however, do really lie 

 superimposed upon each other, and the one divides for the passage of the other, much as 

 in the human species. The interlacing of the tendons of the different flexors is exceedingly 

 intricate. Almost every one sends tendinous slips to one or more of the others ; so that 

 the most simultaneous action of all the toes is secured ; and though the fleshy bellies of 

 some of the tendons have diverse origins, the combined effect of the whole seems to be 

 that of a single powerful flexor. 



Explanation of Plate V. 



Fig. 1. — Superior aspect of skull. 

 Fig. 2. — Lateral aspect of skull. 

 Fig. 3. — Inferior aspect of skull. 



Figs. 1, 3, are without the inferior maxillary. These three figures are of the natural size. 

 Fig. 4. — Pelvis and posterior extremities in situ. One half the natural size. 



Published November, 1866. 



