MYTILUS MUSCLE. 189 



from {AtmXo? (mutilos) the diminutive of pv$ 

 (mus) a mouse. Some of the species have their 

 base elongated with lobes on each side, and bear 

 a resemblance to a bird in full flight.* The 

 name Mytilus is now confined to the shells 

 whose beaks are terminal. 



MYTILUS Edulis. f 



COMMON MUSCLE. 



Specific Character. Shell oval, pointed at the 

 beaks ; sides much sloped, flattish at the an- 

 terior, and rather angular and carinate at the 

 posterior end ; hinge terminal ; beneath the 

 margin are several tooth-like crenulations ; colour 

 often of a rich blue when deprived of its epider- 

 mis which is brown; inside blue about the 

 margin, and whitish in the middle, length from 

 two to three inches, and about half as broad. 



This shell is the most common of all the 

 British species, and is found in large beds, 

 attached by a byssus. The mollusks have a 

 tongue-shaped muscular foot, capable of great 

 powers of elongation and contraction ; with this 

 instrument they are able to effect a progressive 

 motion. Forming a furrow in the sand, and 

 placing their shell erect, they stretch out the 

 foot, which being rather viscid, adheres to the 

 ground, and when an effort is made to contract it, 



* Plate X. figure 3. t Plate X. figure 2. 



