160 
CONCHIFERA. 
Avicula. 
Tho Coal Measures, Bradford, Leeds, and Coalbrook Dale. 
2. Avicula Oweni.— Owen’s Avicula, pi. LXY. fig. 13. 
Nearly orbicular, very much compressed, with large unequal 
ears, which are destitute of striae; surface with numerous, 
rather close, divergent stria;, and a few distant, distinct lines 
of growth ; sides plain. 
Differs from the preceding in the valves being perfectly 
straight. In the Museum of the Manchester Natural History 
Society, and named in honour of its Secretary. 
Hie Coal Measures, Vale of Todmorden. 
3. Avicula simili. —The Similar Avicula, pi. LXY. fig. 
12 . 
Nearly orbicular; cars very large, with transverse oblique 
radiated stria), and longitudinal, nearly obsolete ones ; hinge¬ 
line a little triangular ; surface smooth, with divergent strim, 
and remote indistinct lines of growth, one side with tho ear 
and margin straight. 
The Coal Measures, Yale of Todmorden. 
4*. Avicula plicata. —The Plicated Avicula, pi. LXY. 
fig. 8. 
A early orbicular; somewhat oblique ; the valves much com¬ 
pressed ; hinge-line somewhat triangular; ears largo, unequal, 
with divergent, transverse, distinct stria;, crossed by wider 
curved striae ; one ear concave on the side ; whole surface with 
numerous radiating strict, crossed by remote, indistinct ones; 
margins even. 
The Coal Measures, Middleton, near Leeds. 
5. Avicula iiemispii^ekica. —The Hemispherical Avicula, 
pi. LXY. fig. 5. 
Pecten kemisphmrica. Phillips, Geo. York, II. p. 212, 
pi. 0, fig. 16. 
Nearly orbicular; the lower valve circular and very con¬ 
vex, with tho sides gradually passing into the undefined ears; 
hinge-line straight and a little oblique; surface with squa- 
mose stria?. 
The Carboniferous Limestone, Holland. 
6. Avicula ketroflexa. —The Bent-back Avicula, pi. 
LXYI.* fig. 17. 
A. retrojiexa . Sowerby, Sil. Syst. II. p. 609, pi. 5, fig. 9. 
Short, very broad, semicircular, oblique, somewhat convex, 
transversely wrinkled; anterior ear very small, length 10 
lines, breadth 1 inch. 
The l pper Ludlow Rock, Hale-end, Melverns, near Usk. 
7. Avicula costata.— The Ribbed Avicula, pi. LXYI.* 
figs. 7, 8, 9. 
A. costala. Sowerby, III. p. 77, pi. 244, fig. 1. 
Deeper valve transversely ovate; auricles nearly equal; 
surface with eight smooth, longitudinal, curved, divergent 
ribs, with internal furrows corresponding to the external ribs, 
which project beyond the margin; shallow valve nearly fiat, 
with numerous external rays, the posterior auricle of which 
is separated from the shell by a deep narrow sinus, and pro¬ 
vided with a few sharp teeth on the sides under the auricle, 
tho opposite auricle large, much elongated and acute, extend¬ 
ing considerably beyond the body of tho shell. 
The Cornhrash, Stoney Stratford. 
8. Avicula in.equivalvis.— The Unequal-valved Avicula, 
pi. LXVL* figs. 5, 6. 
A. in(vquivaicis . Sowerby, 111. p. 78, pi. 244, fig. 2. 
Deeper valve obliquely elliptical, convex, enveloping the 
smaller valve, and furnished with a large projecting auricle, 
which is a little rounded at the point ; surface with thir¬ 
teen narrow, divergent, rounded ribs, projecting beyond tho 
margin, and striated in the interstices; flatter valve a little 
convex, smooth, with divergent furrows; posterior auricles 
of both valves very small; substauce of the shell extremely 
thin. 
There are two varieties of this fossil, the oue with strong 
and the other with slender stria). 
The Kelloways Rock, Kelloways; the Inferior Oolite, 
Durslev and Blue TV ick; and the Lias in many localities. 
9. Avicula obliqua.— The Oblique Avicula, pi. LXVI * 
fig. 23. 
A. obliqua. Sowerby, Sil. Syst. pt. II., p. 635, pi. 20, fig. 4. 
Elongated, obliquely ovate, convex, smooth ; hinge-line 
rather short, auricles undefined. Length 1-J inch. 
This species occurs in clusters in the Caradoc Sandstone, 
Soudley, near Acton Scott, east flank of Cuer Caradoc. 
10. Avicula echinata. — The Spinous Avicula, pi. 
LXYI.** figs. 9, 10, 11. 
A. echinata. Sowerby, III. p. 75, pi. 243. 
Obovate, gibbose, a little longer than wide, deeper valve 
with numerous muricated ribs, and unequal auricles, the ante¬ 
rior one is nearly rectangular ; flatter valve generally wider 
than long, smooth, with the anterior auricle acute. 
The Cornhrash, Atford, and Chippenham, the Great 
Oolite, Bath, and the Lias, Yorkshire. 
11. Avicula lanceolata. — I he Lanceolate Avicula, pi. 
LXIX. fig. 3. 
A. lanceolata. Sowerby, VI. p. 17, pi. 512, fig. 1. 
Extremely lengthened transversely, very flat; obliquely 
linear, lanceolate, and compressed ; its width about six times 
its length ; posterior auricle large and obtusely angled, extend¬ 
ing to about one-third tho breadth of tho shell; the anterior 
auricle minute and pointed; beaks placed near the anterior 
extremity. 
The Idas, Lyme Regis, Dorsetshire. 
]2. Avicula ovata.— Tho Ovate Avicula, pi. LXYI.** 
fig. 18. 
A. ovata. Sowerby, YI. p. 18, pi. 512, fig. 2. 
Couvex, transversely ovate; posterior side elongated and 
obtuse ; hinge-line long, occupying more than half of the shell, 
forming part of the posterior wing, which is somewhat obscure. 
The Great Oolite, Stonesfield. 
13. Avicula media. — The Medium Avicula, pi. 
LXXX1I1. figs. 19,20. 
A. media. Sowerby, I. p. 13, pi. 2. 
Ovate, compressed; auricles large, unequal, one large and 
acute ; hinge-line lengthened and parallel; surface smooth. 
The London Clay, Ilighgatoand Sheppy. 
14. Avicula like at a. —The Lineated Avicula, pi. LXYI * 
fig. 10. 
A. lineata. Sowerby, Sil. Syst. pt. II. p. 610, pi. 5, fig. 10. 
Obliquely ovate, compressed, surface with many radiating 
elevated lines; anterior auricle minute, posterior one well 
marked, triangular, half as long as the posterior side. Length 
nine lines; width one inch and two lines. 
Tho Upper Ludlow Rock, near Ludlow. 
