402 ON AVIAN OSTEOLOGY. 



The obliquity of the foraminal passage for the ambiens is 

 easily made out, its higher aperture being on the inner aspect of 

 the bone, and situated, as I have pointed out above, far back 

 from the antero-internal border of the bone. To best appreciate 

 the fa,ct that this sesamoid in P. pelagicus is formed as I have 

 demonstrated it to be in Cormorants of all species, it shoiild be 

 viewed from above rather than from either side or in front. 



EXPLANATION OF PLATE LXI. 



[All the figures are reproductions of photogi-aphs made by the author direct from 

 the specimens. Each bone is of natural size, and from an adult individual. They 

 are from skeletons in the Collections of the U.S. National Museum, the Museum 

 numbers of which are given under the figures.] 



Fig. 1. Right patella of Nannoptemm Iiarrisi; antero-lateral aspect. (No. 

 19719.) 



2. Left patella of N. harrisi ; mesial or inner aspect. (No. 19719.) 



3. Right patella of PJialacrocorax penicillatus, antero-lateral aspect, or the 



same view in which fig. 1 is shown. (No. 18535.) Note that the 

 foraminal passage for the ambiens has been entireh' absorbed. 



4. Left patella of P. penicillatus ; inner aspect. (No. 18535.) 



5. Left patella of PAaZacrocora.u jozmctetes; inner aspect. (No. 18282.) 



6. Left tibio-tarsus of P. punctatus ; anterior view, with the patella articulated 



in situ. (No. 18282.) 



7. Right tibio-tarsus, anterior view, of Flialacrocorax magellanicun, with 



patella articulated in situ. (No. 18438.) 



8. Left patella of P. magellanicus; inner surface. (No. 18438.) Note that 



the exit of the foraminal passage points to the fact that it is in the 

 verj' last stages of its ultimate disappearance. This is an interesting 

 link in the chain of evidence on the real composition of this bone in the 

 Phalacrocoracidae. 



9. Proximal extremitj^ of tibio-tarsus and fibula of right pelvic limb of 



Flialacrocorax iirile; adult. (No. 19655.) Outer aspect, with patella 

 and femur articulated in situ. 



10. Inner aspect of the bones composing the knee-joint of P. urile ; partly 



ligamentous. (No. 18982.) Right pelvic limb. 



11. Left patella, tibio-tarsus and fibula (superior moieties), anterior aspect ; 



left pelvic limb of P. urile. (No. 18982.) Note the complete union 

 and the continuation of the rotular channel of the tibio-tarsus on the 

 anterior face of the patella. 



12. Right patella of Flialacrocorax vigua ; outer surface. (No. 18479.) 



Note groove leading down from the foraminal opening. 



13. Left tibio-tarsus of P. vigua (No. 18479), with patella articulating 



in situ. 



14. Bones of the knee-joint of Flialacrocorax auritus ("P. dilophus," 



No. 19262.) Right pelvic limb, inner aspect. Femur somewhat 

 displaced, but patella properly articulated. 



15. Bones of the knee-joint of P. auritus (No. 19262) ; left pelvic limb, outer 



aspect and articulated in situ. Note the line of demarcation between 

 the true patella and the anterior part of the bone, which originally 

 belonged to the tibio-tarsus. 



16. Anterior aspect of the proximal extremities of the left tibio-tarsus and 



fibula of Flialacrocorax albiventris, with the patella duly articulated 

 above them. (No. 18437.) The rotular channel is very broad in this 

 species and rounded above. 



17. Right patella, inner surface of P. alhiventris. (No. 18437.) The foramen 



is almost closed up. 



18. Bones entering the knee-joint of Flialacrocorax jielagicus, adult, nat. size. 



Right pelvic limb, outer aspect. Ligamentous preparation with femur 

 slightly luxated. Patella in situ. (No. 19032.) 



19. Skeleton of the knee-joint of P. pelagicus. (No. 19032.) Left limb, 



outer aspect ; patella in situ. 



