104 THE LIFE OF CRUSTACEA 



They have usually very small eyes, which appear 

 as if they were not of much use for vision ; and 

 some of the hinder pairs of legs are short, and 

 carried folded against the sides of the body, probably 

 for use when the animal is moving up or down in its 

 burrow. 



Most of the Stomatopoda resemble the Thalas- 

 sinidea in their mode of life, and show some curious 

 similarities to them in structure, although by no 

 means closely related. They are described as lying 

 in wait for prey at the mouth of their burrows, 

 darting out on passing fish or other animals, which 

 they seize with their great saw-toothed claws, and 

 retreating with great rapidity to the bottom of the 

 burrow. 



Most of the Crustacea mentioned live below tide- 

 marks, and at all events are rarely seen when the 

 sand in which they burrow is left bare by the tide ; 

 but there are others, especially on tropical shores, 

 which seem to have their chief period of activity 

 when the sand or mud banks on which they live are 

 exposed to the air. Chief among these amphibious 

 forms in the warmer seas are the Crabs of the genera 

 Ocypode and Gelasimus and some of their allies. 



Some of the species of Ocypode .(Plate XV.) dig 

 their burrows between tide-marks, where they are 

 swamped by the advancing tide, and must be ex- 

 cavated afresh when the water retreats. Other 

 species, however, live above high-water mark, and 



