INTRODUCTION. 



Intestinal simple, naked, destitute of limbs. 



Mollusca, simple, naked \ but not without limbs. 



Testacea, animal with a calcareous covering. 



Lithophyta, animal composite, affixed to, and fabricate a calcareous 



base. — CoraL 

 Zoophytdy a vegetating stem like a plant \ animal composite, and 



resemble flowers. 



Linnaeus has included in the Testacea Order the whole tribe of 

 Shells. In the generic characters he regards both the Shell and its 

 inhabitant: in the definition of species, the former only is attended 

 to. There are very strong arguments against the method of arrang- 

 ing this tribe by the Animals, although it cannot be denied, that the 

 Shells are only the coverings or habitations, and should not demand 

 our primary attention *. 



The Testacea are Vermes of the soft and simple kind, and are 

 covered with a calcareous habitation. These are separated into three 

 divisions, according to the number of valves of which the Shell con- 

 sists. The first division includes only three genera, Chiton, Lepas, 

 and Pholas ; these are called Multivalves, and are formed of many 

 valves,, or pieces, disposed transversely on each other. The second 

 division consists of Bivalves, or Shells of two pieces, connected toge- 

 ther with a hinge, or cartilage. The third division is of Univalves, 

 and have the Shell complete in one piece, as the word implies. The 

 Linnsean genera are — 



* Vide Donovan's Instructions for collecting and preserving. Subjects of Natuxai 

 History. London, 1794, 



