322 



Prof. G. Elliot Smith. 



[Jan. 15, 



The mere fact of its co-existence at this stage with the knot, 

 necessarily occasions some reconsideration of the morphological 

 relationship of the mammalian primitive streak to the process of 

 gastrulation. 



" The Brain of the Archaeoceti."* By G. Elliot Smith, M.A., M.D., 

 Fellow of St. John's College, Cambridge, Professor of Anatomy, 

 Egyptian Government School of Medicine, Cairo. Communi- 

 cated by Professor G. B. Howes, LL.D., D.Sc., F.E.S. Re- 

 ceived January 15, — Read February 12, 1903. 



So far as I have been able to ascertain, nothing whatever is known 

 of the form of the brain or, more strictly, of the cranial cavity in 

 the Archreoceti. Hence no apology is needed for presenting even this 

 imperfect account of two cranial casts representative of this sub-order, 

 which have come into my hands. 



Among the Eocene remains found in the Fayum region of the 

 Egyptian desert by Mr. H. J. L. Beadnell and Dr. Charles W. 

 Andrews, in 1901, there was a broken skull of Zeuglodon, j from which 

 it was possible to obtain a mould, representing the form of the greater 

 part of the dorsal and lateral aspects of the brain. A plaster cast was 

 made in the British Museum at the instance of Dr. Andrews, who 

 kindly placed it at my disposal for description. 



In the following winter (1902), Mr. Beadnell found in the same 

 locality a natural cranial cast of the same size and general form as the 

 artificial cast of Zeuglodon. It is obvious at a glance, if the two 

 specimens be placed side by side, that the natural mould belongs to 

 some member of the Archieoceti, but whether to the same species or 

 even genus as the other specimen must at present remain an open 

 question. 



Mr. Beadnell kindly placed this specimen at my disposal. 



The size and relative proportions of the different parts are almost 

 identical in the two casts. Nevertheless, there are a considerable 

 number of differences, some features being displayed in one and not in 

 the other, and vice versa. Many of these differences are obviously due 

 to the imperfections of the casts, and especially to the failure of the 

 plaster mould to represent the true form of the brain. But there are 



* These notes were : originally intended for the Beport on the Survey of the 

 Fayum, to be issued by the Egyptian Survey Department, and are now published 

 separately with the permission of the Under Secretary of State for Public Works 

 and Captain H. G. Lyons, Director- G-eneral of the Survey Department. 



f C. W. Andrews, " Extinct Vertebrates from Egypt," Part II. (Extracted from 

 the * Geological Magazine,' N.S., Decade IV, vol. 8, 1901, p. 437, — Zeuglodon, Osiris, 

 Dames'.) 



