60 FEBRUARY. 



as your fist. Ugly, uncouth, bemired, the valves not 

 nearly containing the shapeless flesh, they are not par- 

 ticularly attractive creatures, maugre the brilliant hue 

 of their blushing siphons. Like Mrs. Merrifield's 

 Pholas, these Saxicavse habitually break into one 

 another's houses, as we see here, and even cut one 

 another's shells and bodies through and through most 

 ruthlessly. They will live very well out of the rock, 

 and may be kept a considerable time in the aquarium. 



There is no doubt that the burrowing Mollusca are 

 slowly but surely effecting changes in the configuration 

 of rocky coasts, by destroying the rock. It is true their 

 excavations extend but a few inches in depth ; but then, 

 as the force of the elements readily breaks down the 

 thin partitions left standing, and discovers a new face, 

 so the borers are continually renewing their attacks on 

 this ; and so in time the cliffs are worn away, while the 

 debris of impalpable mud is deposited upon the shallows, 

 entering into new combinations, and filling up estuaries 

 and harbours. 



