29 
W. carinata. It is easy to connect together all the Cretaceous 
and Jurassic species of carinated Waldheimias, hut well marked 
forms distinguish different horizons. A new genus Aulacothyris 
has recently been formed by Douville to include the carinated 
Waldheimias. If the range of a species he increased and new 
genera he rapidly formed, we shall find that only names are 
altered, the term species will disappear, and the only 
division will he genera and varieties. 
