114 MOLLUSCA. MYTILID.E. Lithodomus. 



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



suddenly raised above the posterior ; posterior lobe irregular — Soiver. Min. 

 Conch, t. ccx. £ 3, A.— Iron Sa7id. Fig. 4. if from Carbonifei-ous Limestone 

 near Cardiff, will yet rank as a distinct species. 



8. M cBqualis. — Oblong, convex, smooth, anterior lobe large, obscurely de- 

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



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



rounded, posterior lobe small, distinct — Sower. Min. Conch, t. ex. f. 5, 6, "]. 

 — Lias. 



10. M. cvjwata 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. Isl. gihhosa Elongated, reniform, very gibbose, smooth; back broad, 



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



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



expanded; posterior lobe smaW.— Sower. Min. Conch, ccsii. f. 1, 2, 3 — Infe- 

 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. 

 JNIin. 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. 



16. M. plicata. — Transversely elongated, slightly curved; back nearly 

 straight, plaited obliquely — List. Conch, t. Dxxi. f. 76. 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 — Soiver. Min. Conch, t. ccxlviii. f. 2 — In Lias. 



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

 small ; anterior lobe flattisli ; 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. Uthophagus. — Cuticle green, finely striated by the 

 layers of growth ; inside glossy^ iridescent. 



Mytilus lith. Linn. Syst. i. 1156. Soiver. 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. 



