INTRODUCTION. 



43 



rendered uneven by raised knobs, it is said to be tuherculated ; 

 and if rendered rough and prickly by sbarp points it is muri- 

 cated, as in the cut, fig. 97- The term reticulated is applied 

 to fine raised lines, crossing each other, and resembling fine 

 net work. 



External surface. Fig. 91, cancellated; 92, cm'onatecl ; 93, imbricated ^ 



94, pectinated ; 95, plicated ; 96, decussated ; 97, muricated ; 



95, foliated. 



By the foregoing general observations and explanations, it 

 is trusted that the reader will be prepared for the following 

 exposition of the general arrangement of Lamarck, and the 

 principles upon which it is founded. 



GENERAL ARRANGEMENT 

 ACCORDING TO LAMARCK. 



In Lamark^s '^Histoire Naturelle des Animaux sans Ver- 

 tebres,'^ he divides the invertebrata into classes, the 9th, 10 tii 

 and 11th of which include animals possessed of shells properly 

 so called. These are the Annelides, the Cirripedes, the 

 CoNCHiFERA, and the Mollusca. 



The class Annelides constitutes the 9th, and is divided 

 into three orders, namely, the " Apodes," " Antennees," and 

 "Sedentaires/' the last of which, the Sedentaria, alone contains 

 testaceous animals. This order includes tubular shells, which 



