24 THE SEA-SIDE AND AQUARIUM. 



the day. May not this be the period of roaming for 

 food, as well as when covered with the tide ? 



" The march of the Limpet is slow and formal; and 

 whenever the cupping process is renewed, the poste- 

 rior end of the shell is brought into contact with the 

 rock, which is of a soft nature, and will receive the 

 impressions of its denticulations. The track of an 

 individual placed under surveillance was thus made 

 visible over a space of several yards, possessing the 

 same regularity and disposition, and was further 

 remarkable for the constant revolutions on its left. 



" The tracks of the Limpet on granite and other 

 hard rocks, present, at first sight, the same appear- 

 ances ; but, on a closer examination, they are found 

 to differ. When first observed in 1829, a large por- 

 tion of a fine-grained sienitic rock was traced over 

 by these shells: the remainder was plain, and ap- 

 peared varnished with a thin coating of some kind of 

 fucus, without any markings upon its surface. As 

 no Patellae were at first discovered, and the isolated 

 situation of the rock prevented any from reaching it, 

 I was at a loss to explain these appearances; but, 

 after some search, a fissure was found at the north 

 end, where five or six Limpets had affixed themselves, 

 each having a direct road leading to their pasturage 

 ground. By the help of a glass, the markings visible 

 on the rock were discovered to be the remains of the 

 above fucus, which had been eaten through or trodden 

 down by these animals in their excursions, and which 

 retained the indentures of their shells. The edge of 



