164 MEMOIRS OF THE CARNEGIE MUSEUM 



Neither the ^'rotular channel," nor the popliteal fossa are very deeply excavated ; 

 and on the head of the bone the pitlet for the ligaraentura teres is also quite shallow. 

 The muscular lines of the shaft are distinctly defined both in front and behind. 



AVith its shaft somewhat antero-posteriorly compressed, and very slightly bowed 

 to the front, the tibio-tarsus presents us with pro- and ectocnemial processes well 

 developed, and a cnemial crest that rises above the summit of the bone. Of con- 

 siderable length is the conspicuous ridge for articulation with the fibula, and at the 

 antero-distal extremity of the shaft we observe the presence of the osseous bridge 

 under which the tendons pass in life. This end of the bone inclines as it were to 

 the inner side, so that if the mid-vertical axis of the large internal condyle were 

 extended it would be removed from and parallel to, the longitudinal axis of the 

 shaft, rather than being in the same line with it. 



Both extremities of this bone, as is the case with the extremities of the tarso- 

 metatarsus, are m.ore or less massive and enlarged as compared with the shafts of 

 the same. Coming to the fibula, it is very interesting from the fact that it is com- 

 plete, rather more so if anything than we find it to be in either Pandion or Urinator, 

 and is only anchylosed to the tibio-tarsus by means of its enlarged and extreme 

 distal end. This limited fusion of the two bones takes place at a point just above 

 the external condyle. 



Anhinga has a large patella, but proportionately not as large as we find it in the 

 Cormorants. It is an oblong sesamoid, nearly equilateral, concave behind and 

 convex anteriorly, where it is transversely perforated by a minute foramen for the 

 passage of the ambiens muscle. 



As will be seen from measurements above, the tarso-metatarsus is relatively a short 

 bone of the leg; it is further characterized by having its somewhat broad shaft com- 

 pressed in the antero-posterior direction and marked longitudinally upon both 

 aspects by strong muscular and tendinal lines and grooves. The hypotarsus is 

 strongly developed, especially the interno-lateral part of it, which, by a plate-like 

 extension, has a firm attachment to the upper third of the shaft. Its posterior angle 

 above is alwaj^s thickened and doubly pierced for tendons. The externo-lateral part 

 of the hypotarsus is small and it also creates by its form a groove and a foramen for 

 certain tendons that pass through or over them during the life of the individual. 



One or two small foramina pierce the upper part of the shaft in an antero-pos- 

 terior direction, the most constant one making its exit behind to the inner side of 

 and at the base of tlie hypotarsus. At the distal end the trochleas for the toes 

 stand well apart. The inner one of the three is the lowest, and juts out in a prom- 

 inent way from the bone, and has a tubercle projecting from its lateral aspect. 



