Terebratula. mollusc a. ACEPHALA. 369 
Length nearly an inch and a quarter ; breadth one inch, convex, of a black- 
ish horn-colour ; sides abruptly turned in, and flattened, and marked with a 
few irregular striae ; front margin a little indented on each side, and project- 
ing in the middle ; perforation somewhat triangular. 
368. T. aurita. — Regularly ribbed ; the large valve broadest 
in the middle, semicircular in front, and becoming narrow at the 
apex. 
Flem. Phil. Zool. li. 498. t. iv^ f. 5. — T. costata, Lowe^ Zool. Joum. ii. 
105. t. V. f. 8, 9. — West coast of Scotland. 
Length about breadth /oths of an inch ; whitish ; the ribs, from the 
beak to the margin, the most distinct, rounded, and about eight in number, 
obsoletely wrinkled concentrically ; the ribs, towards the sides, indistinct ; 
margin crenulated by the ribs ; the small valve nearly orbicular ; the hinge 
margin subtruncated, or rather obtusely angular, and having the sides de- 
pressed ; inner surface punctated ; peduncle short, of numerous unequal and 
tubular threads attached to a complicated tendino-muscular apparatus, and 
chiefly to the lower valve. I obtained a small specimen of this species at 
Ullapool, in Loch Broom. The one, of a larger size, described by Mr Lowe, 
was found by Mr J. Berkely, at Oban. 
EXTINCT SPECIES. 
* Margin of the valves entire^ or slightlg waved. 
1. T. suhrotunda. — Circular, depressed, smooth ; valves regularly and equal- 
ly convex. — Sower. Min. Conch, t. xv. f. 1, 2.— In Chalk. 
2. T. owato.— Ovate or oblong-ovate, depressed, smooth ; small valve flat- 
tish, slightly pentangular — Sower. Min. Conch, t. xv. f. 3 — In Green Sand. 
3. T. punctata — Oblong, depressed ; valves equally convex ; edge straight- 
ened at the front ; the whole surface finely punctated — Sower. Min. Conch, 
t. xv. f. 4 — In Lias, 
4. T. carnea. — Depressed, smooth, obtusely five-sided ; front edge short ; 
valves equally convex, slightly flattened along the middle — Sower. Min. 
Conch, t. XV. f. 5, 6. — In Chalk, 
5. T. Nearly circular, depressed, smooth; valves equally gib- 
bous ; front margin straight or slightly depressed in the middle, with one un- 
dulation on each side of it.~-~Sower. Min. Conch, t. xv. fi 7- — In Chalk. 
6. T. intermedia — Obscurely five-sided, rather depressed, smooth ; larger 
valve most convex ; front margin undulated ; three depressions in the smaller 
valve, and two in the larger. — Sower. Min. Conch, t. xv. f. Q.— Green Sand. 
7. T. semiglobosa ^Nearly circular, gibbous, smooth ; largest valve deepest, 
and uniformly gibbous; front margin undulated, with two risings in the 
smaller valve. — Sower. Min. Conch, t. xv. f. 9.— In Chalk. 
8. T. biplicata. — Oblong, gibbous ; beak prominent ; sides rounded ; front 
straightish when full grown, elevated with two distant large plaits. — Sower. 
Min. Conch, t. xc. and t. ccccxxxvii. f. 2, 3.— -In Green Sand. 
9. T. digona. — Triangular, oblong, gibbous ; beak prominent ; sides round- 
ed ; front either convex or concave ; when old, bounded by two prominent 
angles, alike in each valve. — Sower. Min. Conch, t. xcvi. — Oolite. 
10. T. ouoicfes.— .Ovate, elongated ; beak prominent; larger valve gibbous, 
VOL. I. 
A a 
