302 MYTILUS. 



Avicula. Enc. Method, t. 177. f. 4. 



Variety C. Less scaly and whitish, with dark blue longitudi- 

 nal rays. 



Favanne, t. 41. f . E 1. Enc. Meth. t. 177. f. 1 and 2. 

 Chemnitz, xi. p. 250. t. 198. f. 2015. 



Inhabits the East and West Indian Seas. Linn&us. Coasts of 

 Jamaica. Lister. Amboyna. Rumphius. China and Ota- 

 heite. Humphreys. 



Full grown shells are sometimes ten or twelve inches long, and 

 the length rather exceeds the breadth ; these are thick and 

 ponderous, but young shells are thin, brittle, and slightly 

 eared; the margin is rounded, except on the side of the 

 hinge, where it is straight and transverse ; the colour is com- 

 monly greenish or pale chestnut, sometimes marked with 

 paler rays, and Chemnitz has figured a beautiful Variety with 

 dark blue rays. This species affords valuable pearls, and 

 the inside (which is known by the name of Mother of Pearl) 

 is beautifully polished and iridescent. 



radiatus. 5. Shell roundish, with transverse mem- 

 branaceous scales, forming spinous processes 

 arranged in longitudinal lines. 



Mytilus margaritiferus, Var. Chemnitz, viii. p. 134. t. 80. 



f. 719. 

 Avicula radiatus. Leach Zool. Misc. i. p. 98. t. 43. 

 Avicula. Enc. Meth. t. 177. f. 3. 

 Knorr, ii. t. 25. f. 2 and 3. Favanne, t. 41. f. E 3. 



Inhabits the coasts of Tranquebar. Chemnitz. 



Shell about two inches and a quarter long, and two inches 

 broad, of a greyish colour, with a few obsolete or sometimes 

 purplish rays ; it is nearly allied to M. margaritiferus, and 

 differs principally in being armed with regular longitudinal 

 rows of thorn-like processes which issue from its transverse 

 membranes. 



unguis. 6. Shell roundish, longitudinally striated, 

 pellucid, and slightly eared. 



Mytilus Unguis. Linncsus Syst. Nat. p. 1156. Gmelin, 

 p. 3351. 



Inhabits the Mediterranean. Linnaus. 



Linnaeus describes this shell to be about the size of a man's 

 nail, very thin and transparent, and finely striated longitudi- 

 nally ; no subsequent author has ascertained the species, but 

 it is generally supposed to belong to the Ostreee. 



