Cope.] ^^ [August 15, 



As this paper goes to press, the interesting announcement made at the 

 meeting of the British Association for tlie advancement of science at 

 Montreal may be referred to. Mr. Caldwell, the holder of the Balfour 

 scholarship, telegraphs that he has discovered that the Platypus anatinus 

 is oviparous, and that the egg is meroblastic. This confirms the hypothesis 

 of descent Irom reptilian ancestors rather than Batrachian. Haeckel gives 

 the segmentation as meroblastic, Studien zur GastraeaTheorie, Jena, 1877, 

 p. 65. 



Note on the Tarsus. — I am just in receipt of an MS. from Dr. Baur, 

 of New Haven, in which he presents an identification of the "internal 

 navicular" bone of some rodents, and which probably existed in the ungu- 

 late genera Pantolambda and Bathmodon. He identifies it with the tibiale, 

 and denies that the astragalus includes that element, but that it consists 

 wholly of the intermedium. This identification will also apply, though 

 Dr. Baur in his manuscript does not make it, to the element which sup- 

 ports the spur in the known Monotremata. It will also explain the nature 

 of the element which occupies the same position in the foot of the Pelyco- 

 sauria above described. The arrangement in this order of reptiles con- 

 firms the conclusion reached by Dr. Baur, since the questionable element 

 is here in direct contact with the tibial facet of the astragalus. 



Note on Phylogeny of the Vertebrata. — As my researches have 

 now, as I believe, disclosed the ancestry of the Mammals,* the birds, •)• 

 the reptiles, and the true fishes,:}: or Hyopomata, I give the following phy- 

 logentic diagram illustrating the same. This will only include the lead- 

 ing divisions. The special pliylogenies of the Batrachia |1 and Reptilia,§ 

 and some of the Mammalia "[[ have been already given. 



The Mammalia have been traced to the Tlieromorphous reptiles through 

 the Monotremata. The birds, some of them at least, appear to have been 

 derived from tlie Dinosaurian reptiles. The Replilia in their primary rep- 

 resentative order, the Theromorpha, have been probably derived from the 

 Rhachitomous Batrachia. The Batrachia have originated from the sub- 

 class of fishes, the Dipnoi,:}: though not from any known form, I have 

 shown that the true fishes or Hyopomata have descended from an order of 

 sharks,:]: the Ichthyotomi, which possess characters of the Dipnoi also. 

 The origin of the sharks remains entirely obscure, as does also that of the 

 Marsipobranchi. Dohrn** believes the latter class to have acquired its 



* American Naturalist, 1884, p. 1136. 



t Proceedings Academy Philadelphia, 18G7, 234. 



X Proceedings American Philosophical Society, 1884, p. 585. 



li American Naturalist, 1884, p. 27, 



2 Proceedings American Association for the Advancement of Science, xix, 

 1871, 2S3. 



If Proceedings American Philosophical Society, 1882, 447; American Naturalist, 

 1884, p. 261 and 1121. Report U. S. Geol. Survey W. of 100th Mer., G, M. Wheeler 

 1877, iv, ii, p. £82. 



** Der Ursprung der Wlrbelthiere u. d. Princip des Functionwechsels, von 

 Anton Dohrn, Leipsic, 1875, p. 32. 



