Teigonia. MOLLUSCA. TRIGONIADiE. 405 
11. T. jomwato.— Oblong, transverse, with concentric costae; along the 
middle of the anterior side is a ridge from which many tuberculated ridges 
diverge each way— 5'owen Min. Conch, t. ccxxxvii. f. 6. — In Green Sand. 
1 2. T. elongata. — Elongated, gibbose, subtriangular ; anterior side obtuse, 
transversely costated ; posterior side separated from the anterior by a cre- 
nulated carina, bicarinated, longitudinally striated, striae granulated.— S'owcr. 
Min. Conch, t. ccccxxxi. — Upper Oolite. 
13. T. nodosa Obovate, depressed ; anterior part covered with rows of 
large knobs, a portion of the posterior part plain ; superior edge straight.— 
Sower. Min. Conch, t. Dvii. f. 1. — In Gre^n Sand. 
14. T. imbricata Transversely oblong, depressed ; with five or six con- 
centric dentated, subimbricated keels upon the rounded anterior side ; pos- 
terior side obliquely truncated, ribbed. — Sower. Min. Conch, t. Dvii. f. 2, 3. 
-•mOolite. 
15. T. cuspidata Obovate, depressed, ribbed ; posterior side truncated, 
its lower angle pointed ; ribs concentric, with projecting angles where they 
pass into the posterior side. — Sower. Min. Conch, t. Dvii.. — Oolite. 
16. T. angidata Transversely elongated, convex ; posterior side produced, 
truncated, transversely striated, bounded by a crenulated line ; the remain- 
der ornamented with nodose ridges, bent at right angles as they pass over the 
middle — Sower. Min. Conch, t. Dviii. f. -Under Oolite. 
1 7* T. Obovato-triangular, with transverse smooth ribs ; posterior 
side obliquely truncated, marked with several crenulated ridges, and bound- 
ed by a strong crenulated keel ; lunette large, regularly striated across. — 
Sower. Min, Conch, t. Dviii. f. 2, 3. — In Oolite. 
18. T. spectahilis, — Suborbicular, rather elongated, convex, nearly smooth, 
ornamented with about seven bent rows of large round tubercles upon the 
anterior side, and a few small ones scattered over the posterior side ; one row 
of compressed tubercles upon the posterior slope. — Sower. Min. Conch. t.Dxliv. 
— In Green Sand. 
Gen. CI. AVICULA. — Shell flat, oblique unequivalve, un- 
equilateral ; transversely produced in a straight line at the 
base, where the sides are lobed, and the beaks rather re- 
mote ; hinge linear, with a single tooth in each valve un- 
der the beaks ; ligament linear external. 
412. A. hirundo . — With the tail as long as the wing. 
Turt. Biv. Brit. 220, t. xvi. f. 3. — On the southern coasts of England 
and Ireland. 
Length 2 inches, breadth nearly the same ; smooth, or slightly scaly with 
the layers of growth, but, under a lens, it appears finely punctured ; colour 
green or brown ; inside pearly. It was first observed, as a native, by Miss 
Hutchins, in Bantry Bay ; and announced as British by Mr Sowerby in his 
Min. Conch, i. 14. 
EXTINCT SPECIES. 
1. A. wedia.— Ovate, depressed ; wings large unequal, one wing acute, 
valves nearly equal ; length of the shell and hinge nearly equal ; surface 
smooth.— Min. Conch, t. n.-^London, Clay. 
