216 A BOOK OF- WHALES 



amount of union has been observed in two specimens 

 of M. bidens. In M. layardi the first three vertebrae 

 were united, the rest free. The high spines of the 

 dorsal and lumbar vertebrae, and the absence of a slope 

 backwards in those vertebral spines allies the present 

 genus to Zip kins and Hyperoodon, and distinguishes 

 it from Berardius. Zygapophyses extend to about 

 the sixth vertebrae (dorsal) in M. australis, further 

 back to the tenth in M. grayi. The lumbar vertebrae 

 are strongly carinate below. There are eleven chevron 

 bones, judging from the presence of articular facets. 

 The sternum has five distinct pieces in the immature 

 M. grayi ; only four in the adult M. australis. In 

 both there are notches between the successive ele- 

 ments, which are naturally converted into foramina. 



While there is a great uncertainty about' the species 

 of Zip kiits more is known, thanks to the studies of 

 Sir W. Flower, concerning the species of this genus 

 Mesoplodon. Eight species, at any rate, can be clearly 

 recognised, mainly by the position and the characters 

 of the teeth. 



These eight species, with their synonymy,* are as 

 follows : 



Mesoplodon bidens, Sowerby ;]- (j= DelpJiimis {Heter- 

 don} soiverbiensis, Blainville ; D. sowerbyi, Desmarest ; 

 Delpkinorkynckus micropterns, Cuvier ; Mesoplodon 

 sowerbiensis, van Beneden ; Micropteron bidens, 

 Malm ; Aodon dalei, Lesson). 



* This synonymy only relates to the specific names. 

 t British Miscellany, p. i. 



