56 OUTLINES OF NATURAL HISTORY. 



the fact that there springs from the mouth a jjair of long, 

 tiexible, fleshy processes, which carry numerous filaments 

 on one side, and are closely coiled up into a spiral (fig. 

 22, D, a). These singular processes are partially sup- 

 ported by the shelly loop (fig. 22, B, I) already spoken of 

 as existing in the smaller valve of the shell. They are 

 termed the "arms," and it is by their instrumentality 

 that particles of food are brought to the mouth. The 

 animal possesses a well-developed stomach (s), and an in- 

 testine, the latter terminating blindly. There is also a 

 large liver {h). The nervous system consists of a central 

 mass placed near the gullet. 



Terebratula flavescens inhabits the seas of Australia, 

 and lives a sedentary life, being attached to submarine 

 objects by means of a muscular stalk which passes through 

 the aperture in the beak of the larger valve of the shell. 



Recapitulation of Essential Characters. — Animal 

 included in a bivalve shell. The valves of the shell 

 very markedly different in size (sometimes very slightly 

 so), and placed over the back and front of the animal. 

 Shell attached to some submarine object by a muscular 

 stalk (sometimes by the shell itseK). Mouth furnished 

 with a pair of long, spirally-coiled, fringed processes or 

 " arms." These characters distinguish the class of the 

 Brachiopoda as a whole. 



CHAPTER XVI. 

 class lamellibranchiata. 



This division includes the numerous animals commonly 

 known as " Bivalve shell-fish," such as Cockles, Mussels, 

 Oysters, Scallops, and the like. These animals derive 

 their common name from the fact that they have the body 

 protected by a shell, which is composed of two pieces or 



