INVERTEBRATE ANIMALS. 79 



Group 183.— Genus NEPTUNUS (De Haan) and allies. 

 Many of the species of this group are found on the 

 high seas far from land. Note the clean-cut lines of the 

 shield, the arms, and the swimming-paddles in the 

 frigate-like Neptunus iielagicus. The form of this ocean- 

 crab is a study in the art of combining prehensile 

 efficiency with strength and speed. 

 Estimated number of species : recent, 20 ; British, 0. 

 IT Examples of Amphitrite, Oceanus crucifer, &c. 



Group 184.— Genus PORTUNUS (Fabricius) and allies. 

 The British Swimming-crabs are known to fishermen 

 by various local names, such as the common Shore-crab, 

 the Velvet-crab, the Fiddler-crab, the Nipper, &c. They 

 are not first-rate swimmers, but are active and voracious, 

 and from their omnivorous propensities have been termed 

 the scavengers of the sea. 



Estimated number of species : recent, 30; British, 12. 

 H Examples of Scylla, Polyhius, Portumnus, &c. 



Group 185.— Family EPJPHID^ (Dana). 



Mr. Dana has established this family to include 

 certain crabs distinguished by some important peculi- 

 arities connected with the respiratory apparatus. The 

 small but pretty species of Trapezia, with bright porcel- 

 lanous shields, are found amongst the branches and 

 folia of living corals. 

 Estimated number of species : recent, 60 ; British, 2. 



H Examples of Eudora, Pilumnus, Galene, Domcetia, 

 Geryon tridens, &c. 



Family CANCERIDiE. 

 Group 186. — Genus CANCER (Linnaeus). The generic 

 name Cancel' has been retained to include the common 



