264 ZOOLOGY. 



irregularly toothed : *** Apex recurved, pointed : **** 

 Entire^ notpointed at the Apex : **"***^/jex perforated. 



Limpets abound on rocky coasts, and may be found in 

 great abundance, adhering to rocks and stones ; the fresh 

 water species attach themselves to aquatic plants, they all 

 affix themselves so tenaceously, that it is with difficulty they 

 are remored without injury. 



33. Dentalium.. Tooth-Shell. Inhabitant a Terrebella. 



Shell nearly strait, slender, tubular, mostly pervious. Plate 

 5, fig. 33. 



These shells are all marine, they may be found on sandy 

 beaches at low water, generally in a perpendicular or oblique 

 direction, beneath the sand or mud, and are discoverable by 

 a slight depression on the surface. 



34. Serpula. Worm-Shell. Inhabitant a Terrebella. 



Shell slender, tubular^ usually adhering to other substances, 

 often divided iniernally by imperforate partitions, at 

 irregular distances, pla'e 5, fig. 34, There are two 

 fariiilie"! m 'he genus : * Flexuous^ irregular in shape, 

 and adherliig to other sjbstauces : ** assuming a de- 

 termined form, and detached. 



Like the last genus, these are confined to the ocean, and 

 are often foaxi 1 in considerable numbers, attached to other 

 shells J stoaes, and plants. 



