894 The Number of Bones at present known, etc. [November 



a lighter companion, the fibula, on its outer side. Up to the pres- 

 ent date I know of but two free bones that occur about the knee- 

 joint; the first of these is the patella, and this may co-exist with 

 the, cnemial ridge of tibia, as in Colymbus (Owen). The other is 

 a free sesamoid found in some birds, in a notch at the head of the 

 fibula (Speotyto). In at least one bird the head of the tibia, or 

 rather its proximal extremity, may be formed by an epiphysis so 

 large as to include in the young the extensive pro and ecto- 

 cnemial ridges {Cinclus mexicanus). The fibula is never so far 

 produced as to articulate with the tarsus or its elementary repre- 

 sentatives. Young birds of several genera offer us for examina- 

 tion at the distal end of the tibia, three distinct ossifications that 

 eventually amalgamate with that bone and with each other. 

 These have been described by Morse and afterwards by myself in 

 the osteology of the Tetraonid^e, as the fibulare (outer one), the 

 tibiale (the inner one) and the intermedium (above). In many 

 birds , i. e., Centrocercus, we find a large sesamoid in the tendons 

 at the back of the joint formed by the tibia and tarso-metatarsus. 

 Three bones unite to form the bone of the so-called tarsus of 

 birds ; they are the second, third and fourth metatarsals, and in 

 immature birds we find their proximal extremities covered by an 

 epiphysis, the centrale of Morse, that may represent the united 

 bones of the distal row of tarsus. This epiphysis may rest just 

 on the summit of the united metatarsals and not include 

 that process found at the upper and posterior aspect of the 

 bone tarso-metatarsus, the much disputed " calcaneal * process 

 (Centrocercus), or it may dip down behind and completely 

 include it (Cinclus). This fact will obviously do away with my 

 terming this process the tendinous, as I did in my osteology of 

 Lanius, and leave quite a knotty point for ornithologists to settle 

 in the way of serial homologies. The first metatarsal is found 

 articulating on the lower and outer edge of the inner metatarsal as 

 the os metatarsale accessorium. A small sesamoid may be found 

 beyond the trochlear of the tarso-metatarsus, as in Eremophila. 

 The number and arrangement of the phalanges in the feet, as 

 found in the various families and orders of birds is too well 

 known to enter upon in so short a sketch as this simply pretends 

 to be. The greatest, and at the same time the most usual num- 

 ber of separate joints, is fourteen, distributed in the order, 2, 3- 4. 

 5, running from first to fourth toe respectively. Among other 



