162 H. SPENCER HAREISON. 



Mr. Swimierton, who have generously placed at my disposal 

 all the slides and preparations made for their research on the 

 development of the skeleton, and who have also granted me 

 the privilege of examining their manuscript and figures. 

 My thanks are also due to Professor Howes for suggesting 

 this research and for the use of a table in his laboratory, 

 and to Mr. M. F. Woodward for much friendly criticism and 

 advice. 



Historical. 



The first account of the adult dentition of Hatteria is that 

 given in 1867 by Giinther (1), where he emphasises the acro- 

 dont character, and points out the important part played by 

 the edges of the dentigerous bones when the teeth have be- 

 come worn down. He gives a full account of the macro- 

 scopic features of the dentition of the adult, but appears 

 to have examined no individuals with vomeriue teeth. He 

 also describes a young specimen (seven inches long) in 

 which each of the premaxillary teeth of the adult was repre- 

 sented by two, and each of the large anterior mandibular 

 teeth by three separate teeth. In this young specimen he 

 could distinguish no polished surface on the "alveolar^' 

 edges, but does not speak positively on this point. 



The discovery of the occurrence of vomerine teeth was 

 made by Baur (2) in 1886. His specimen was 210 mm. in 

 length, and had a tooth on each vomer. 



In 1890 Professor Howes (3) examined nine specimens for 

 vomerine teeth. In five of these no such teeth were to be 

 found; in one they were bilaterally symmetrical, in one the 

 last traces could be detected, in one there was a tooth on the 

 right side only, and in another the right tooth was lai-ger 

 than the left. In no case did they project into the cavity of 

 the mouth. Even when teeth were wanting he found a ridge 

 of the mucous membrane in the proper position on the vomer. 

 He suggested finally that the vomerine teeth are vestigial 

 structures, and are undergoing suppression from left to 

 right. 



