On the Tarsus mid Carpus of Birds. 141 



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VIII. — On the Tarsus and Carpus of^ Birds. (Plates iv, v.) 



By EDWARD S. MORSE, Pii. D. 

 Rend January 29tli, 1872. 



Among the many interesting features of structure, com- 

 mon to birds and reptiles, that have been pointed out from 

 time to time by Huxley, Gegenbaur, Dana and others, that 

 point which established the existence of tarsal bones in 

 birds, with the joint occurring between the first and second 

 tarsal series as in reptiles, seems the most important. 



There is still, however, a variance of opinion as to the 

 number and condition of the tarsal and carpal bones in 

 birds, and upon this question I hope to throw some little 

 light. 



The most important contribution has been made by 

 Gegenbaur,* who has shown the presence of two tarsal 

 bones in the embryo chick, which unite, respectively, with 

 the distal end of the til)ia and the proximal end of the 

 metatarsus, leaving the ankle joint l)etween the proximal 

 and distal tarsal series, as in reptiles. In the upper tarsal 

 bone he figures two centres of ossification, and from what 

 he finds in certain reptiles, believes that these two centres 

 in the cartilaginous mass indicate the presence of two 

 tarsal elements, the astragalus and calcaneum. 



In referring to other authors, I find a great difierence of 

 opinion respecting the existence of any tarsal bones. Prof. 

 Owen, who has contributed so hirgely to our knowledge of 

 the osteology of birds, particularly the larger and more 

 aberrant forms, such as Ap)teryx, Binornis, ^pyornis and 



*TJntersuchuugen zur Vergleicliendea Anatomic der Wirbelthiere. Erstes Heft 

 Carpus uud Tarsus. Leipzig, ISOi. 

 March, 1872. 10 Anx. Lyc. Nat. msT., Vol. x. 



