38 THE ELEMENTS 



carii and JBeccarii per versus, two 

 shells, the principal distinction of 

 wliich, is the contrary turn of their 

 volutions, it is easily determined, by 

 the convexity of the upper side ; and 

 of course, the aperture beinoj placed 

 somewhat beneath." Testacea Bri- 

 tannica, page 3.52, &c. 



Chambers are the divisions formed 

 by partitions, at regular intervals ; as 

 in the Nautilus. Plate 3d, &g. llth, 

 WW WWW. 



In some of the Serpula there are 

 also divisions, but they are not regular 

 as the preceding; and they differ from 

 the Nautilus, in wanting a Siphuncu- 

 lus or communication between the 

 chambers ; the animal forms a com- 

 plete partition and adds to its shell, 

 which it would appear to be necessi- 

 tated to do, from its body growing 

 too large for its abode. 



Several of the Patella genus, have 

 chambers of a laminiform, subspiral. 



