BIVALVE SHELLS. 45 



side pearly shining green. One and a half inch wide. In- 

 habits the British seas 



Anomia Ephippium. — The Saddle Anomia. Plate I. 

 fig. 7. Shell suborbicular, irregularly wrinkled, and waved; 

 upper valve convex, under flat and perforated at the hinge, 

 through which the ligament passes by which it is affixed to 

 other bodies ; inside perlaceous, and of various changing 

 colours; green, purple, violet, or yellow. 



Often to be met with adliering to the common oyster, or Ostrea 

 maxima. 



a Base, m ligament perforation. 



The AnomiiB inhabit the ocean. The animal attaches itself to fuel, 

 shells, stones, and other extraneous bodies at the bottom of the sea : 

 they are generally affixed by a testaceous plug, which adheres to one 

 of the muscles of the aiumal and passes through the perforation in 

 the flat valve. 



Genus 16— MYTILUS. 



Animal allied to an Ascidia; shell bivalve, rough, gener- 

 ally affixed to other bodies by a byssus or beard of silky 

 filaments ; hinge mostly without teeth, having a subulate, 

 excavated, longitudinal line. Plate VII. fig. 16. 



The Linnaean Mytili are divided into three families : * parasitical, 

 affixed as it were by claws, as exempUfied in the Mytilus Crista Galli ; 

 ** flat or compressed into a flattened form, and slightly eared ; as in 

 the Mytilus margaritiferus ; *** elongated, ventricose, or convex, as 

 in Mytilus edulis. 



Mytilus edulis. — The Edible Muscle. Plate II. fig. 

 4 and 6. Shell oblong, pointed at the beak, sides much 

 sloped ; anterior side a little angulated ; smooth, and radi- 

 ated with deep blue or purple ; covered with an umber- 

 coloured epidermis; inside, round the margin, of a fine blue, 

 which grows gradually lighter towards the centre ; cicatrix 

 very distinct and glossy ; beneath the beak are several 

 crenulations, which some have supposed to be teeth. 



This is the most common shell we have, and well known 

 by the name of Muscle or Mussel. It forms a pleasant and 

 nutritious food. They have, however, in some localities, 

 proved poisonous, and fatal consequences have followed 



