INVERTEBRATE ANIMALS. 67 



and rocky pools reflect a rich flush of iridescent purple 

 extending over the whole body, heightening in efi"ect the 

 various streaks and spots of orange, light-blue, red, 

 chestnut, and cream -white which adorn the animal. 

 These disappear, though the animal may continue in 

 health, after a few hours' exposure to the Hght; and 

 specimens captured from shallow pools have even when 

 first taken all their markings of a pale-olive tint. 

 Estimated number of species, 42 (M. Edwards); 

 British, 11 (Bell). 



^ Examples of Rhynchocinetes, Hippolyte, and 



Palcemon, including P. carcinus and P. Jamai- 



cencis. 



Group 168.— Families CKANGONID^, ALPHEID^, and 



PEN^IDiE. Shrimps, Crangon, exhibit a tendency 



the reverse of that noticed in Prawns, the species found 



in Northern Seas being frequently larger than those 



belonging to the more southern coasts of Britain. In 



the Arctic seas and in the bays of Spitzbergen they 



supply food to the Walrus and the Seal (Adam White). 



Estimated number of species : recent, 52 ; British, 10 



(Bell). 



IT Examples of Crangon, Atya, Sicyonia, Alpheus, 

 including Crangon borealis. 



This group, together with the preceding = Famille 

 des Salicoques (M. Edwards). 



Jfiftteitt^ Cabk Cass* 



The Mark % indicates specimens or other illustrations exhibited in the Cases. 



Group 169.— Families THALASSINID^ and ASTACI- 

 BM, excluding Homarus. The former of these famiHes 

 includes the burrowing Macroura, generally found buried 



