(52 A HISTOBY OF EECENT CEUSTACEA 



If the tiny young of the Crustacea attack and destroy 

 one another, it is not for want of innumerable other enemies 

 fitted to keep their numbers in check. As far as tbe 

 timidity of human experience can decide, the Crustacea in 

 general, though by no means particular as to the food they 

 consume, invite rapacity by the agreeable quality of the 

 food they supply. The enormous spines of the very young 

 and the strong armature of the adults have probably been 

 called into existence in consequence. Where these are 

 wanting or inadequate, the life of the species has been 

 protected by extreme fertility. In Geryon guinquedens, 

 Smith, for example, it has been computed that one speci- 

 men was carrying no less than forty-seven thousand eggs, 

 and there are other species reckoned to be at least twice as 

 prolific. 



To the extensive genus Xantho Bell assigns three 

 British species, naming them florida, rivulosa, and tuh&r- 

 culata. But, Montagu's floridus having lapsed as a syn- 

 onym, the first of the three should be named Xantho 

 incisus, Leach. The second, on Bell's own showing, ought 

 to be called Xantho hydropliilus (Herbst), and of this 

 Couch's tuberculata is now held to be a variety. 



Ozius, Milne-Edwards, 1834, was a genus established 

 to receive certain species found in the Indian and Austra^ 

 lian waters. The name had been given much earlier by 

 Dr. Leach, but without published description. It presents 

 a peculiarity by help of which the large family of the 

 Cancridae is divided into two sections. The space between 

 the front margin of the buccal frame and the mouth itself 

 was called by Milne-Edwards the prelalDial space. By 

 English writers it is called the endostome or palate. In 

 Cancer, Xantho, and many other genera, this endostome is 

 without distinct longitudinal ridges defining the apertures 

 of the efferent branchial channels, whereas in Oziua, Piluwr 

 nus, jEriphia, and others, it has these ridges. 



Pseudozius, Dana, 1851, is, as the name implies, a 

 genus that might be mistaken for Ozius, but the crests of 

 the endostome do not quite reach the upper margin of the 

 buccal frame. In 1881 the species Pseudozius Mellissi 



