366 On Complete Fibulce in existing Birds. 



1"5 centimetre of the lower periphery of the outer tibial 

 condyle '^ ('Science/ vol. ii. no. 41, p. 642). Upon ex- 

 amining other skeletons of this species I find that it often 

 comes much nearer than this to heing quite complete, and I 

 doubt not but what examples, sooner or later, will be found 

 of this Cormorant wherein the fibulae ossify for their entire 

 lengths. 



In Sula jnscator (see fig. 2, p. 365) the fibula is also appa- 

 rently complete; but in the adult the fact is quite marked, due 

 to the very thorough fusion which takes place between it and 

 the tibio-tarsus at its lower fourth. Still, in most specimens 

 of this Gannet it can be distinctly traced, the distal fibular end 

 being made evident by the existence of a slight enlargement 

 seen immediately above the distal tibial epiphysis. No fusion 

 of the articulations of the fibula with the other leg-bone 

 takes place above this point. In Sula cyanops a similar con- 

 dition exists as in S. piscator, and the fibula can even be 

 more distinctly traced for its entire length. The case is 

 better still in the Common Gannet [S. bassana), where the 

 distal end of the fibula reaches down to the sutural trace 

 of the union of the tibia with the co-ossified tarsal element. 

 This is also the case in Sula gossi and other species of 

 Gannets which I have examined in regard to this point. 



In Fregata aquila the fibula is also complete, and in some 

 specimens only its extreme distal end fuses with the tibio- 

 tarsus ; and it also reaches down to the tarsal element. 

 Among the Steganopodes departures are seen from this con- 

 dition of affairs, both in Pelecanus and in Pha'ethon (two 

 species). In these genera, apparently, the fibula is never 

 complete, especially in the latter genus. In Pelecanus fuscus 

 it is entirely free from the tibio-tarsus and much shorter 

 than that bone ; in Pha'ethon it fuses with it at a point about 

 halfway down its shaft. 



