Avictla. 
CONCH I FEU A. 
161 
15. Avicula reticulata. —The Reticulated Avicula, pi. 
LXVI.* fig. 20. 
A . reticulata. Sowerby, SiL Syst. pt. II. p. 014, pi. 6, fig. 3. 
Oblong ovate, oblique, one valve rather convex, and the 
other nearly fiat; botli pointed towards the beaks, and broad 
at the base; surface with numerous, longitudinal, divergent 
ribs, decussated by rather strong lines of growth ; auricles un¬ 
equal ; one hardly developed, the other very large and rectan¬ 
gular. 
Aymestry Limestone, Croft Valley, Aymcstry; Lower 
Ludlow, Myddleton Hall, Wenlock Limestone, Falfield and 
Tot worth. 
10. Avicula orbicularis.— The Orbicular Avicula, pi. 
LX VI.* fig. 21. 
A. orbicularis. Sowerby, Sil Syst. pt. II. p. 035, pi. 10, fig. 2. 
Nearly orbicular, convex, and almost smooth ; with a few 
almost obsolete lines of growth; beaks produced; auricles 
small, the anterior one round, the posterior not protruding be¬ 
yond the margin; hinge-line straight; length and breadth 
nearly equal. 
The Caradoc Sandstone, Acton Scott, near Caradoc ; 
Honderly and Cheney Longville. 
IT. Avicula Murchisoni. — Murchison’s Avicula, pi. 
LXVI.* fig. IS. 
A. orbicularis Sowerby, Sil. Syst. pt. II. p. 035, pi. 20, 
fig. 3. 
Obliquely elongated, rather inflated, smooth, or with nearly 
obsolete lines of growth, and very obtuse, imperfectly deve¬ 
loped, concentric ridges ; beaks small, acute ; anterior auricle 
very small, its outline undulous ; posterior auricle not pro¬ 
truding beyond the margin; with a very slight obtuse flexuro 
beneath it. 
The Caradoc Sandstone, Acton Scott. 
18. Avicula rectangularis.— The Rectangular Avicula, 
pi. LXVI.* fig. 11. 
A. rectangular is. Sowerby, Sil. Syst. pt. II. p. 603, pi. 3, f. 2. 
Smooth, obliquely sub-triangular, and very convex ; hinge¬ 
line long, straight; anterior side almost straight; posterior 
side produced, in the form of a lobe; front rounded; beaks 
rather acute and slightly turned downwards ; auricles not de¬ 
fined. 
The Old Red Sandstone, Ilorcb Chapel, in the Cwm-dwr, 
between Trecastlo and Llandovery, Wales. 
19. Avicula hum at a.— The Buried Avkula, pi. LXVI.** 
fig. 1. * 
A. obliqua. Brown, Trans. Manch. Geo. Soc. I. p. 225, pi. 7, 
fig. 64. 
Sub-depressed, valves very oblique; hinge-line long, nearly 
straight; surface with numerous elevated, divergent, longitu¬ 
dinal ribs, emanating from the slightly protruding beaks, and 
terminating a little beyond the margin, producing a crenulated 
edge, crossed by many fine lines of growth ; auricles of medium 
size, the anterior one only defined ; length and breadth about 
half an inch. 
The Coal Shale, GTi ms worth and Vale of Todmorden. 
20. Avicula Samuelsii. —Samuels’ Avicula, pi. LXVI.** 
fig. 29. 
A. Samuelsii. Brown, Trans. Manch. Geo. Soc. I. p. 225, 
pi. 7, fig. 65. 
Semicircular, wider than long; hinge-line straight; the 
auricles undefined; beaks small, pointed, and not much pro¬ 
duced beyond the hinge-line; surface covered with rounded, 
longitudinal, divergent ribs, which emanate from the beaks 
and pass over the margin, giving a fine pectinated appearance, 
crossed by numerous distinct lines of growth. Length up¬ 
wards of a quarter of an inch ; breadth, n third more. 
The Coal Shale, High-Green Wood, Vale of Todmorden. 
Named in honour of my friend John Samuels, Esq., of Barton 
House, Manchester, Vice-President of the Manchester Na¬ 
tural History Society. 
21. Avicula Binneyi.— Binney’s Avicula, pi. LXVI.** 
figs. 5, 6. 
A. Binneyi. Brown. Trans. Manch. Geo. Soc. I. p* 65, 
pi. 6, figs. 27, 28. 
Smooth, oblique, beaks prominent, acute; larger auricle 
nearly parallel with the hinge-line and undefined; the other 
small; hinge-line straight; posterior side abruptly contracted ; 
interior side very broad; centre of the valves considerably 
ventricose. Length three-sixteenths of an inch ; breadth 
nearly a quarter of an inch. 
The New Red Sandstone, Newtown, Lancashire. 
22. Avicula inflata. —The Inflated Avicula, pi. LXA L* 
figs. 4 and 8. 
A. inflata. Browu, Trans. Man. Geo. Soc. I. p. 65, pi- 6, 
figs. 25, 26. 
Oblique, inflated, transversely oblong-ovate; hinge placed 
much to one side, where it is narrow and subcompressed, with 
a small and acute auricle, widening rapidly towards the oppo¬ 
site side. Length three-sixteenths of an inch, breadth a quar¬ 
ter of an inch. 
The New Red Sandstone, Newtown, Lancashire. 
23. Avicula tenua. —The Thin Avicula, pi. LXVIII. 
fig. 9. 
P. Brown, Trans. Man. Geo. Soc. I. pi. 5, fig. 23. 
Oblique, compressed ; hinge-line slightly oblique ; anterior 
side nearly straight, with the auricle undefined ; posterior side 
with a considerable curvature under the ear, beneath which it 
is produced and rounded; surface smooth, with irregular in- 
equidistant, concentric, slight wrinkles. 
In the Black Bass, Pendleton Coal Mine, near Man¬ 
chester. 
24. Avicula squamula. — The Scale Avicula, pi. 
LXVIII. fig. 10. 
Oblique, compressed ; hinge-line slightly oblique ; anterior 
side nearly straight; posterior side very slightly curved; 
surlace smooth, with a few nearly obsolete concentric 
wrinkles. 
The Coal Shale, V ale of Todmorden. 
25. Avicula anomala.— The Anomalous Avicula, pi. 
LXVI.* fig. 22. 
A. anomala . Sowerby, Geo. Tr. 2d Ser. IV. p. 342, pi. 17, 
fig. 18. 
Very obliquely elongated, imperfectly five angled, disk 
flattened; beaks acute, protruding beyond the hinge-line, 
which is greatly obliqued; surface with many longitudinal 
narrow elevated ridges, crossed by slightly defined lines of 
growth; valves very deep, together measuring about one and a 
half inch, with a square section ; basal line sub-triangular. 
The Greensand, Blackdown. 
2 p 
