270 THE LIFE OF CRUSTACEA 



Cretaceous epoch onwards. The Brachyrhyncha 

 perhaps begin to appear about the same time, but 

 the affinities of the earlier types are doubtful, and it 

 is only in the Tertiary that they become abundant 

 and unmistakable. Several living genera, such as 

 Cancer, date back to the Eocene. The Spider Crabs 

 (Oxyrhyncha) are rare as fossils, and the earliest 

 specimens are found near the beginning of the 

 Tertiary. 



