324 



POPULAR CONCHOLOGY. 



constructed as to close the hole in the valve when the 

 muscle is contracted. The animal is phosphorescent, and 

 is eaten in France. A. ephippium is a European species, 

 and though eaten in France is considered unwholesome 

 here. Besides this species there are three others British. 



^Enigma. Rock. — Shell distinguished from Anomia 

 by the boss of the upper valve being distant from the 

 edge, and also that from the boss to the edge there is a 

 cleft ; the under valve has on the outside of the cleft a 

 fold from the hole, towards the hinge. — 5 species. 



Five species known in the Chinese seas ; the type is the 

 Tellina cenigmatica of Chemnitz. 



Class V.— BKACHIOPODA. 



The animals forming this class are inclosed in a bivalve 

 shell; the two valves are symmetrical, but not exactly 

 alike, often connected by a hinge, and having no ligament. 

 One valve answers to the ventral side, and the other to 

 the back of the animal ; at times the under one is firmly 

 attached (like the oyster); usually, however, the upper 

 one (seldom the lower) is perforated for the passage of a 

 tendon by which the inhabitant anchors itself. The animal 

 possesses two mantle lobes, which are always completely 

 separated ; these fulfil the functions of lungs, and, more- 

 over, contain the branching ovaries. In the region of the 

 mouth there are two spiral arms, which can be unrolled, 

 and are usually beset with cilia. These extraordinary 

 creatures occupy a lower scale in organisation than the 

 Conchifera, or leaf-gilled animals ; instead of the con- 



