PLATE LV. 



Musculus fluviatilis maximus, profunde strlatus latus ; testa admodum 

 tenui, ex fusco viridescens, interdum rufescens, 

 jntus argenteus. Gualt. 1 . Conch, tab. l.fig. F. 



Mytilus Cygaeus. Swan. Pain. Brit. Zool. No. 78. tab. 67. 

 No. 78. 



Mytilus fluviatilis maximus, admodum tenuis ex fusco viridescens. 

 Cygneus. Da Costa Br. Conch, p. 214. sp. 46. 



This species Is not uncommon in our Rivers, Ponds, &c. but is 

 less frequent than the Mytilus Anatinus, or Small Horse Muscle, which 

 bears some resemblance to it. Mytilus Anatinus is rarely more than 

 half the size of Mytilus Cygneus, is more compressed, and has the 

 cartilage side extended in a straight line to an acute angle at one end. 



The usual length of Mytilus Cygneus is about two or three inches, 

 its breadth five or six Inches. The valves deep, or concave. The 

 outside is wrinkled transversely, and varies in colour according to the 

 state of the Shell. Tlie external covering, or epidermis, is thin, but. 

 strong, and of a greenish colour ; under this the Shell is varied with 

 bright brown, and when the coating is worn off, the whole Shell is 

 pearly. The inside is often rugged with small pearls. 



