Class BRACHIOPODA*. 



Body compressed, of an oval or occasionally a circular form, 

 contained within the two valves of a shell, which are in most 

 cases connected behind by a hinge, but never by a ligament or 

 cartilage. The shell is inequivalve, and furnished inside with 

 a complicated skeleton for supporting the arms, which will 

 be presently noticed. The mantle is divided into two lobes, 

 and its outer edge is fringed with a row of extensile tentacles, 

 every one of which has at its root or base a coloured spot, 

 which may be a rudimentary eye. Each lobe contains a folded 

 or spirally coiled arm, which is furnished with one or more 

 rows of flexible cirri or filaments. The animal is destitute of 

 a head or foot; but it has a slit-shaped mouth behind the 

 arms, an excretory tube, a stomach, several vesicles which 

 serve the purpose of a heart, nerves, muscles, liver, and repro- 

 ductive organs. The circulatory system is supplied by the 

 mantle and arms, there being no gills. It is supposed by some 

 writers that both sexes are united in the same individual ; but 

 this is doubtful. In the majority of cases (e. g. Terebratulidce) 

 the animal is attached to extraneous bodies by a fibrous stalk 

 or peduncle, which is placed at the back, and penetrates the 

 upper or convex valve ; while in others (e. g. Craniidce) it is 

 usually affixed by the outer surface of the lower valve, which 

 is flat. 



This remarkable and peculiar Class is nearly equal in 

 value to the Conchifera (see vol. i.) as regards the im- 

 portance of its structural characters ; and, although it 

 does not contain so many species, they are quite as 

 abounding in individuals. In point of antiquity it is far 

 superior, 



" of ancestry 



Mysteriously remote and high;" 



and not even a Welshman, who would place Adam in 

 the middle of his genealogical tree, can boast such a 



* From an erroneous notion that their feet take the shape of arms. 



B 



