216 LIFE BY THE SEASHORE. 



Fucus, by its numerous sharp-clawed legs, and is extra- 

 ordinarily variable in colour. Usually brown or brownish, 

 it is sometimes tinted with yellow, red, or green, sometimes 

 spotted or striped with darker colour. The length varies 

 from three-quarters of an inch to an inch or more, and the 

 flattened body makes the little creature very inconspicuous. 

 As in other members of the order, the number of rings 

 in the body is primarily the same as in Decapoda, but the 

 body is distinctly divided into three regions, of which the 

 thoracic is the most conspicuous. The first thoracic segment 

 is fused to the head, so that the thorax 

 appears only to possess seven rings ; the 

 abdominal segments are in part fused. 

 The head bears two pairs of antennae, 

 consisting of simple flagella; of these 

 the outer are half as long as the body. 

 There are seven pairs of similar thoracic 

 legs, corresponding to the seven free 

 thoracic segments. Over the surface of 

 the abdomen there is a triangular tail- 

 shield which covers all except the two 

 first rings. The five anterior abdominal 

 FIO. 62. idotea tricuspi- appendages are converted into thin respi- 



data. In part from Bate r i A ,-, ,1 < . 



and Westwood. ratory plates, the sixth pair forms two 



strong valves which cover over these 

 thin plates. In life the valves are in constant motion, 

 opening and shutting to facilitate the passage of water 

 over these curious breathing organs, which replace the gills 

 of the Decapods. A careful dissection of Idotea is easily 

 made, and will be found very profitable. 



The Amphipoda are most typically represented by the 

 sand-hoppers, which swarm everywhere over the damp sand, 

 assembling in myriads about decaying substances thrown on 

 the beach, and perforating the dry sand above high-tide 

 mark in all directions with their burrows. They are the 

 great scavengers of the shore, sometimes within a few hours 

 reducing dead birds of considerable size to the condition of 

 skeletons. On the rocks their place is taken by other forms 

 equally abundant, and of similar habit. 



The common sand-hopper is Talitrus saltator. Like its 

 allies, it presents a general resemblance to the Isopods, but 



