BIVALVE SHELLS. 



Genus 16.— MYTILUS. 



Animal allied to an Ascidia; shell bivalve, rough, generally 

 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 Linneaxi Mytili are diyided into three families : * parasitical, aSxed zs 

 tX were by claws, as exemplified in the Mytilas Crista Galli ; ** flat or com- 

 pressed into a flattened form, and slighted eared ; as in the Mytilus Mar- 

 garitit'erus ; *** elongated, ventricose, or convex, as in Mytilas Eduiis. 



Mytilus eduiis. — The Edible MrscLE. Plate IL fig. 4. and 

 6. Shell oblong, pointed at the beak, sides much sloped ; an- 

 terior side a little angulated ; smooth, and radiated 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 weU known by 

 the name of muscle. It forms a pleasant and nutritious food. 

 They have, however, in some localities proved poisonous, and 

 fatal consequences have followed eating them. The true natiu-e 

 of this poison has not yet been satisfactorily accounted for. 



Plate II. fi?. 4- and 6. a The cartilage, c r length of the shell, u u breadth 

 of the shell, o disk, r r the beak. 



Mytilus Incurvatus. — The Incurvated Mytilus. Plate 

 yil. fig. 16. Oblong oval, nearly smooth, both valves much 

 inflated, and curved on one side near the ligament, apex acute, 

 and base much widened. Inhabits the British coasts. Pro- 

 bably it is only a variety of the Mytilus eduiis. 



It is to the Mytilas Margaritiierus, ,'the Meleagrina margaritifera of 

 Lamarck,} Plate X. fig. 10. that we are indebted for that precioos gem, the 

 real pearL It is an inhabitant of the lodiaa ocean ; where it is regularly 

 fished for by men who dive to the bottom of the sea, in places where it fre- 

 quents, la this periloas employment, the divers are often attacked by 

 shark*, and not anfreqaently lose their lives. — Mother of pearl ornaments 

 £re made from the shell itself. 



The Mytili inhabit the ocean, lakes, rivers and ponds. Marine muscles 

 adhere to rocks or beds by a thin but very tenaceous byssus, consisting of 

 extremely fine and tough filaments, and some to the Gorgoaiae by claws. 

 Some penetrate calcareous and art'ilac<?ons ri ck«, where they reside without 

 changing place, others adhere to mcks or clay on the shore. They are mnch 

 used for bait or food, and as such they are esteemed by many. The fresh 

 water muscles are generally found on the surface, or a little way under the 

 mud. Most species of muscles produce oearls. 

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