MALACOZOA. TKOPIOPODA. LAMELLIBRANCHIATA. 235 



A. Mytilus edulis vulgaris. Common Eatable Mussel. 



Shell oval-oblong, rather thick ; the umhones curved, ap- 

 proxmiated, the anterior dorsal slope slightly convex, forming 

 an obtuse angle with the posterior dorsal, which is nearly 

 parallel to the ventral, the latter slightly undulated ; the hinge 

 margin with three teeth ; the epidermis dusky, the shell blue, 

 plain or radiated with white or yellowish-brown. Length 

 from three to four inches, breadth from an inch and a-half to 

 nearly two, or about half the length. 



In the Estuaries of the Ythan and Dee. 



Muscuhis ex caBruleo niger. Lister, Anim. Angl. 182. PI. 4. f. 

 1S2. — Mvtilus edulis. Linn. Svst. Nat 1157. — Mvtilus edulis. 

 Perm. Brit, Zool. iv. 110. PI. G3l f. 73; Ed. ii. iv. 236. PI. 66. f. 

 2.— Mytilus edulis. Turt. Brit. Biv. 196.— Mytilus edulis. Flem. 

 Brit. Anim. 41 L — Mytilus edulis. Mont. Test. Brit. 159. 



B. Mytilus edulis pellucidus. Thin-shelled Eatable Mussel. 



Shell subovate, thin ; the umbones curved, contiguous, the 

 anterior dorsal slope nearly straight, forming a distinct angle 

 with the posterior dorsal, which inclines considerably toward 

 the ventral, the latter slightly undulated ; the hinge-margin 

 with two teeth ; the epidermis olivaceous or yellowish-brown, 

 the shell whitish with blue rays, 

 inches, breadth more than half the length. 



In the Estuaries of the Ythan and Dee. 



Mytilus pellucidus. Penn. Brit. Zool. iv. 112. PI. 63. f. 75; Ed. 

 n. iv. 237. PI. 66. f. 3.— Mytilus pellucidus. Mont. Test. Brit. 160. 

 —Mytilus pellucidus. Turt. Brit. Biv. 197. PI. 15. f. 1, 2.— My- 

 tilus edulis. Flem. Brit. Anim. 411. 



C. Mytilus edulis incurvdtus. Incurved Eatable Mussel. 



Shell subovate, thick, opaque ; the umbones curved, sepa- 

 rated, the anterior dorsal slope somewhat convex, forming a 

 prominent rounded angle with the posterior dorsal, which is 

 much curved and inclined toward the ventral, the latter straight, 

 or sinuate ; the epidermis dusky, abraded, exposing a great 

 part of the shell, which is pale blue and corroded. From an 

 inch and a-half to two inches in length. 



In clefts of rocks, on all the rocky coasts ; the largest indi • 

 viduals usually solitary in pools. 



Mytihis incurvatus. Pcnn. Brit. Zool. iv. 111. PI. 64, f. 74; Ed. 

 n, iv. PI, 67. f. I. — Mylilus incurvatus. Mont. Test. Brit. 160. — 

 Mytilus incurvatus. Turt, Brit. Biv. 197. — IMytilus incurvatus. 

 Lamk. Syst. vi. 127 ; Ed. n. vii. 48.— Mytilus edulis. Flem. Brit. 

 Anim. 41 1. 



