414 
MOLLUSCA. MYTILIDJ2. Lithodomus, 
7. M. Upartita — Elongated, smooth, rather gibbose ; anterior side obtuse, 
suddenly raised above the posterior ; posterior lobe irregular — Sower. Min. 
Conch, t. ccx. £ 3, 4 . — Iron Sand. Fig. 4. if from Carboniferous Limestone 
near Cardiff, will yet rank as a distinct species. 
8. M cequalis. — Oblong, convex, smooth, anterior lobe large, obscurely de- 
fined. — Sower. Min. Conch, t. cx. f. 2 . — Iron Sand. 
9. M. minima . — Ovato subtriangular, smooth ; front nearly straight, ends 
rounded, posterior lobe small, distinct. — Sower. Min. Conch, t. cx. £ 5, 6, 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..gibhosa — 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 — Infe- 
rior Oolite. 
13. M. imhricata — 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.— 5'ower. Min. Conch, t. ccxii. f. 4 — Inferior Oolite. 
1 6. M. plicata. — Transversely elongated, slightly curved ; back nearly 
straight, plaited obliquely — List. Conch, t. Dxxi. f. 76- Sower. Min. Conch, 
t. ccxlviii. f. 1. — Infcrioi' Oolite. 
17. M. scalprum. ■ — Transversely elongated, slightly compressed, nearly 
smooth ; posterior side small, undefined ; anterior side slightly curved and 
produced— 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.— Min. Conch, t. ccii. — In Oolite. 
Gen. CV. LITHODOMUS. — S'hell 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. 
MytUus lith. Linn. Syst. i. 1166. 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. 
