THE DACTYLE PHOLAS. 561 



hinge. The hinges are folded back, and united by 

 a cartilage j and in the inside, beneath the hinge, 

 there is an incurved tooth. The animal contained 

 in this shell is called an Ascidia. 



The animals of this tribe perforate clay, spongy 

 stones, and wood, while very young; and, as they 

 increase in size, they enlarge their habitation within* 

 and thus become imprisoned. They are always 

 found below high water-mark, and a mass of rock 

 may sometimes be seen wholly perforated by them. 

 They have two orifices or openings capable of elon- 

 gation in the manner of a proboscis : one of these 

 is supposed to be the mouth, and has the faculty 

 of spouting water. Most of them contain a phos- 

 phorescent liquor, of great brilliancy in the dark* 

 which also illuminates whatever it touches or hap- 

 pens to fall upon. 



From the following species the character of near- 

 ly the whole tribe may be collected. 



THE DACTYLE PHOLAS*. 



This is an oblong shell, marked with somewhat 

 spinous stripes. When full grown, it is about an 

 inch and a quarter long, and near five inches broad,. 

 It is of a whitish colour, and, in external appear-* 

 ance, has a distant resemblance to a Muscle. 



The great powers of penetration of these animals, 

 compared with their apparent imbecility, have justly 

 excited the astonishment of philosophers and natu- 



* Pholas dactylus. Lint:, 

 VOL. III. O O 



