36 PATELLA. DENTALIUM. SERPULA. 



Without a regular spire : 5 genera. 



" You are well acquainted with Patella, the 

 limpet : one species of this genus is very com- 

 mon on the rocks by the sea-side. (Plate 1.) 

 In the Patella genus we lose sight of a spire ; 

 the shell is nearly conic, and shaped like a basin. 

 The species are very numerous, exhibiting great 

 variety of form ; the number is two-hundred and 

 forty. 



"The form of Dentalium is easily known. 

 The shell is univalve, nearly straight, tubular, 

 not chambered, and open at both ends. 



*' The species called elephant's-tooth is slightly 

 curved, the colour green, (Plate 1.) It is 

 found in the European and Indian seas. There 

 are only twenty-two species. Dentalium en- 

 tails^ the dog's-tooth, is very common. 



" The Serpula genus is remarkable. The 

 shells are tubular, frequently closed at one end. 

 They are often found in clusters, adhering to 

 rocks, stones, fuci, shells, &c. 



" There is Serpula triquetra upon a pecteii, 

 (Plate 8.) 



" From the appearance of this piece of timber 

 you may form some idea of the devastation com- 

 mitted by the Teredo, or ship- worm. (Plate 

 8.) The shell is tubular and flexuose ; two 



