NOTE ON TEETH OF THE ZIPHIOID WHALE,. 

 MESOPLODON LAYARDIIiQ^AX), EXHIBITED AT 

 THE MEETING OF THE SOUTH AFRICAN PHILO- 

 SOPHICAL SOCIETY, 



On Wednesday, August 29, 1888, 



By Roland Trimen, F.R.S., &c., Curator of the South 



African Museum. 



As long ago as 1865, I made for my predecessor, Mr. E. L. Layard^ 

 outline drawings of the heads of two different species of Ziphioid 

 Whales then in the South African Museum ; and he sent these 

 drawings to the late Dr. J. E. Gray, at that time Keeper of the 

 Zoological Department of the British Museum, who had bestowed 

 much study on the Cetacea. Dr. Gray determined the two whales 

 in question, merely from the drawings and Mr, Layard's notes, to 

 be both new species, and described them in the Proceedings of the 

 Zoological Society of London for 1865 respectively as Ziphius 

 Layardii and Petrorhynchus Capensis. The latter has since been 

 identified with Ziphius indicus, Van Beneden ; but the former (which 

 in the form and development of the teeth is by far the more remark- 

 able) retains its position as a very distinct species, peculiar, so far 

 as known, to Cape seas, and is placed by Prof. Flower (Trans. Zool. 

 Soc. Lond., 1872, vol. viii., p. 211) in Gervais' genus 3Iesoplodon. 



The Ziphioid Whales are most nearly related to the Cachalots 

 or Sperm Whales (as is shown in Prof. Flower's memoir just quoted), 

 but, amongst other distinctions, differ remarkably in the very reduced 

 condition of their teeth, which (confined to the lower jaw) are 

 rudimentary and concealed in the gum, with the exception of one 

 pair (or occasionally two pairs) at or towards the extremity. The 

 whales of this group were evidently numerous in Tertiary times, 

 as their abundant remains in the Crag formation testify ; but at the 

 present time they are certainly rare, only individual (usually stranded) 

 specimens now and then occurring in various parts of the world. 



Mesoplodon Layardii exhibits an extraordinary development of 

 the only two teeth it possesses. They are situated at some little 



