MYTILUS MUSCLE. 189 



minutive of [AV$ (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 Edidis* 



COMMON MUSCLE. 



Specific Character. Shell oval, pointed at the 

 beaks ; sides much sloped, flattish at the anterior, 

 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 epidermis 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, at- 

 tached 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, the shell is drawn 



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



