104 PKOCEEDINGS OF THE AMERICAN ACADEMY 



Five hundred and eigliteentli Meeting. 



February 10, 1863. — Monthly Meeting. 



The President in the chair. 



Mr. Ritchie exhibited and explained his newly-invented 

 compass, designed to obviate the effect of local attraction. 



Professor Hitchcock read the following postscript to his 

 paper communicated at a former meeting. 



Since I presented my paper on Footmarks, in December, I have 

 continued my researches with a large addition of new specimens, and 

 I feel a strong confidence that the following positions may be relied 

 upon. 



1.* The protuberances on the under side of the feet of living animals 

 do not, as a general fact, correspond either to the number of phalanges 

 or of articulations. 



2. In some species, however, there is such a correspondence, some- 

 times showing the number of articulations, and sometimes that of the 

 phalanges. 



3. The hindmost impression in the outer toe of the thick-toed biped 

 animals, described in my Ichnology as birds, was made, not by a 

 phalanx or a joint, but by a heel-bone or a process on the tarso-meta- 

 tarsal bone. 



4. Besides this hindmost impression, however, a more careful ex- 

 amination of specimens has satisfied me that the outer toe had four 

 phalanges besides the ungual, the middle toe three, and tfce inner one 

 two, corresponding to the number in tridactyle living birds. 



5. Still more certain is it that the quadruped Anomcepus, described 

 in the Ichnology, had the same number. 



6. The same is true, without much doubt, in the remarkable feath- 

 ered animal, the Archceopteri/x, lately discovered at Solenhofen. 



7. Hence we cannot distinguish in fossils, as has always been sup- 

 posed, between birds and quadrupeds, by the number of jihalanges in 

 their feet. 



8. Hence there is as much reason to suppose that some of the fossil 

 footmarks were made by birds, as there is for putting Archceopteryx 

 into that class, as has been done by eminent zoologists. These old ani- 

 mals, both the fossil and the Lithichnozoa, must have differed a good 

 deal in their anatomical structure from birds, lizards, and marsupials ; 



