Mr Blackmore on the Remains of Birds' Eggs. 75 



eggs, and find them both in texture and size to correspond 

 closely with the eggs of the Commo7i Wild Duck. In colour 

 the shell is rather darker than the larger one, but is in parts 

 similarly incrusted both inside and out. This was found in 

 Mr Harding's pit in November 1862, about 20 feet below the 

 surface, in undisturbed clay. No bones accompanied this 

 specimen/' 



/. On Parallel Relations of the Classes of Vertebrates, and 

 on some Characteristics of the Reptilian Bii^ds, 



II. The Classification of Animals based on the Principle of 

 Cephalization. No. I. By James D. Dana. Communi- 

 cated by the Author.* 



I. On certain parallel relations between the classes of Vertebrates^ 

 and on the bearing of these relations on the question of the dis- 

 tinctive features of the Reptilian Birds. 



At the close of an article by Professor Hitchcock, a portion of 

 a letter of the writer is quoted, in which a parallelism is drawn 

 between the Ootocoid or semi- oviparous Mammals {JMarsupials 

 and Monotremes), the Ichthyoid Keptiles (Amphibians of De Blain- 

 ville, Batrachians of many authors), and the Reptilian Birds. The 

 general fact of this parallelism throws light on (1.) the classifica- 

 tion of Mammals, (2.) the distinctive features of the Beptilian birds, 

 and (3.) the geological progress of life. 



1. Classification. — The Amphibians are made by many zoolo- 

 gists an independent class of Vertebrates, on the ground of the 

 fish-like characteristics of their young. The same systematists, 

 however, leave the Marsupials in the class of Mammals, notwith- 

 standing their divergencies from that type. The number of classes 

 of Vertebrates, usually regarded as foin-, thus becomes five, namely, 

 Mammals, Birds, Beptiles, Amphibians and Fishes. There are 

 some indications that this number will soon be further increased 

 by some zoologists, through the making of another class out of 

 the Reptilian Birds. '\ 



The discovery of the Beptilian Birds has brought the general 

 law to view, that, among the four classes of Vertebrates, ordinarily 



^' From tlie American Journal of Science and Arts, vol. xxxvi., Nov. 1863. 



t Professor Agassiz, in vol. i. of his " Contributions to the Natural History 

 of the United States," page 187, subdivides Fishes into four classes, namely, 

 1. Myzonts ; 2. Fishes proper, or Teliosts (Ctenoids and Cycloids) ; 3. Ganoids ; 

 4. Selachians ; which would make the total number of classes of Vertebrates 

 nine. 



