414 MOLLUSCA. MYTILIMJ. Lithodomus. 



7. M. biparlita. — Elongated, smooth, rather gibbose ; anterior side obtuse, 



suddenly raised above the posterior ; posterior lobe irregular Sower. Min. 



Conch, t. ccx. f. 3, 4 — Iron Sand. Fig. 4. if from Carboniferous Limestone 

 near Cardiff, will yet rank as a distinct species. 



0. M cequalis. — Oblong, convex, smooth, anterior lobe large, obscurely de- 

 fined — Sower. Min. Conch, t. ex. f. 2 Iron Sand. 



9. M. minima. — Ovato subtriangular, smooth ; front nearly straight, ends 

 rounded, posterior lobe small, distinct — Sower. Min. Conch, t. ex. f, 5, G, 7. 

 —Lias. 



10. M. cuneata — Elongated, convex, smooth ; anterior part cuneated ; 

 back arched ; front slightly concave ; posterior side distinct, convex, — Sower. 

 Min. Conch, t. ccii. f. 1. — Inferior Oolite. 



11. M. giblosa — Elongated, reniform, very gibbose, smooth; back broad, 

 arched. — Sower. Min. Conch, t. ccii. f. 2. — Inferior Oolite. 



12. M. reniformis — Oblong, subreniform, smooth ; anterior lobe slightly 



expanded; posterior lobe small. — Sower. Min. Conch, ccxii. f. 1, 2, 3 Infc- 



rior Oolite. 



13. M. imbricata — Oval, elongated ; with imbricated ridges upon the sur- 

 face ; back angular, front concave — Sower. Min. Conch, t. ccxii. f. 1, 2, 3 



Inferior Oolite. 



14. M. Hillana — Depressed, elongato-ovate, concentrically striated ; pos- 

 terior end narrow ; front slightly concave ; posterior lobe obscure. — Sower. 

 Min. Conch, t. ccxii. f. 2 Lias. 



15. M. aspera. — Ovate elongated, posteriorly pointed ; very gibbose, lon- 

 gitudinally striated ; striae elevated, rough, very numerous ; posterior lobe 

 obscure, wrinkled, small — Sower. Min. Conch, t. ccxii. f. 4 Inferior Oolite. 



] 6. M. plicala. — Transversely elongated, slightly curved ; back nearly 

 straight, plaited obliquely — List. Conch, t. Dxxi.' f. 7G. Sower. Min. Conch, 

 t. ccxlviii. f. 1. — Inferior Oolite. 



17. M. scalprum. — Transversely elongated, slightly compressed, nearly 

 smooth ; posterior side small, undefined ; anterior side slightly curved and 

 produced — Sower. Min. Conch, t. ccxlviii. f. 2 In Lias. 



18. M. aliformis.— Triangular, inflated ; back straight ; posterior lobe very 

 small ; anterior lobe flattish ; central part convex, elongated, with projecting 

 beaks — Sower. Min. Conch, t. ccii.— In Oolite. 



Gen. CV. LITHODOMUS.— Shell subcylindrical, rounded 

 at both ends ; beaks nearly terminal ; no teeth ; ligamental 

 line nearly straight. 



423. L. lithophagus. — Cuticle green, finely striated by the 



layers of growth ; inside glossy) iridescent. 



Mytilus lith. Linn. Syst. i. 1156. Sower. Linn. Trans, viii. 270. t.- vi. 

 f. 1, 2, 3, 4, 5 — In cavities of Limestone. 



The specimens in my possession are about an inch in length, and four- 

 tenths broad. At first, this species adheres by a byssus, which ceases to 

 grow after a lodgment in the stone has been effected ; the calcareous matter 

 of which frequently adheres to the surface of the shell like a crust, or becomes 

 attached to the retral extremity in a beak -like process. 



