Leptvena. 
MOLLUSCA. 
123 
12. Leptjsna transversalis. —The Transverse Leptama, 
pi. LIV. fig. 2, 3. 
Leptcena transversalis . Dalman, 1. c. p. 109? pi. 1> fig* 4. 
Ib. Hist. Pet. p. 69, pi. 20, fig. 5. Sowerby, Sil. Syst. p. 629, 
pi. 13, fig. 2. 
Semicircular, greatly convex; lesser valve concave ; hinge 
inflected, with its line parallel, and equal to the width of the 
shell; surface with wide-set, longitudinal ribs, and fine interme¬ 
diate strire. Length seven lines; width somewhat more than 
eight lines. 
Wenlock Shale, Tame Bridge and Hay Head, near Walsall; 
Build was Bridge; Burrington; and Stumps Wood, near Led¬ 
bury. 
13. Leptcena minima —The Least Leptacna, pi. LIV. 
fig. 6, 7. 
Leptcena minima. Sowerby, Sil. Syst. p. 629, pi. 13, fig. 4. 
Semicircular; hinge line parallel, very greatly inflated; with 
numerous, sharp, alternately long and short, smooth, radiating 
ribs; sides a little prolonged, and auriform. Length two lines; 
breadth three lines. 
Wenlock Shale, Burrington. 
14. Leptjrna laevigata. — The Smooth Leptama, pi. 
LIIL* fig. 35. 
Leptcena laevigata, Sowerby, Sil. Syst. p. 629, pi. 13, fig. 3. 
Semicircular, depressed; hinge line parallel, its sides pro¬ 
longed into short, auriform processes; surface smooth, shining, 
with a few radiating stria?, and small, obscure, concentric undu¬ 
lations; base slightly depressed. Length two lines and a half; 
width, exclusive of the prolonged sides, four lines. 
Wenlock Shale, Burrington, near Ludlow. 
15. Lept/ENA sericea. —The Silky Leptama, pi. LIII.* 
fig. 23, 24. 
Leptcena sericea. Sowerby, Sil. Syst. p. 636, pi. 19, fig* L 
Leptcena slriatella ? Dalman, 1. c. p. Ill, pi. 1, fig. 5. 
A transversely elongated semicircle; larger valve convex, 
the other much depressed, or nearly flat; base considerably 
deflected at the margin; surface with a silky lustre, and very 
numerous, close-set, radiating striae, a few of which are deeper 
than the others; some obscure, concentric lines of growth. 
Length five lines; breadth ten lines. 
Muck resembling L. lata> but the striae are finer and more regular 
sided, and the base more parallel. 
Lower Silurian Rocks at Whittingslow; Horderley, Guils- 
field, &c. 
16. Leptcena lata. —The Broad Leptama, pi. LIV. fig. 
19, 20. 
Leptcena lata. Von Buch. Sowerby, Sil. Syst. II. p. 603 
and 610, pi. 3, fig. 10 b and 12 c, and pi. 5, fig. 13. Ure, Hist. 
Ruth, and Kil. p. 317, pi* 16, fig. 10, 11. 
Semicircular, with a rather straight base; upper valve convex, 
slightly depressed in the middle; lower valve concave; covered 
exteriorly with fine, radiating ridges; hinge line parallel, pro¬ 
vided with from eight to ten tubular, simple, divaricating, thin, 
tapering, acute spines. Length half its width. 
This is one of the most characteristic and abundant species of the 
Upper Ludlow Rock. 
Found in the Old Red Sandstone at Felindre, Horeb Chapel; 
in the Upper Ludlow Rock, Ludlow Promontory; Delbury; 
Munslow; Woolhope Valley; Bagnor Hill; Presteign; and 
Lawrieston, near Rutherglen, Renfrewshire. 
17* Leptcena complanata —The Even Leptama, pi. 
LIV. fig. 12. 
Leptcena complanata. Sowerby, Sil. Syst. p. 636, pi. 20, 
fig. 6. 
Semiovate, somewhat shorter than wide, much compressed ; 
hinge line slightly arcuated, and rounded on both extremities; 
beak a little produced; surface with numerous, fine, radiating, 
linear stria*, which increase in number towards the margin, 
crossed towards the base by undulating lines of growth ; base 
deflected. Length eleven lines; width one inch. 
Lower Silurian Rocks at Acton Burnell, Shropshire. 
18. LepT/ENA duplicata. —The Double-plaited Leptama, 
pi. LIV. fig. 13. 
Leptcena duplicata. Sowerby, Sil. Syst. p. 636, pi. 22, fig. 2. 
Semicircular, transversely elongated, convex; inside of valves 
with longitudinal furrows, arranged in pairs. Length five lines 
and a half; width nine lines. 
Lower Silurian Rocks, Cefn, near Welshpool; and Robeston 
Wathen, Pembrokeshire. 
19* Lept2BNA tenuistriata —The Thin-striated Lep¬ 
tama, pi. LIII.* fig. 12. 
Leptcena tenuistriata . Sowerby, Sil. Syst. p. 636, pi. 22, 
fig. 2 a. 
Semicylindrical, with very numerous, close-set, longitudinal 
striae, crossed by from twelve to fourteen slight, concentric, 
convex furrows; sides expanded. 
Closely allied to L. depressa, but the stria? are much finer and closer. 
Lower Silurian Rocks, Norbeth and Marloes Bay, Pembroke¬ 
shire ; and in the Cardoc Limestone, Gaerfawr, Montgomery¬ 
shire. 
20. Leptjena distorta— The Distorted Leptama, pi. 
LIII* fig. 2, 3, 4. 
Leptcena distorta. Sowerby, Min. Conch. VII, p. 10, pi. 
615, fig. 3. 
Irregularly orbicular, convex; hinge line parallel, with a tri¬ 
angular area; beaks prominent; concentrically undulated, with 
strong, longitudinal, interrupted striae; margins flattened. 
Distinguished from L. analoga by its prominent beak, near to which 
it is not compressed, and very convex valves. 
Carboniferous Limestone, Isle of Man. 
21. Lept/ena ambigua. —The Ambiguous Leptama, pi. 
LIV. fig. 16. 
Producta depressa. Phillips, Geo. York. II. p. 215, pi. 8, 
fig. 18. 
Compressed; hinge line nearly parallel; beaks very slightly 
produced; deeper valve concentrically angulated; whole surface 
covered with rather strong, smooth, longitudinal, divergent 
striae; crossed by flexuous, rounded ribs, on the flat surface. 
Mountain Limestone, Florence Court. 
22. Leptcena plicatilis _The Plicated Leptaena, pi. 
LIIL* fig. 6. 
Producta plicatilis. Sowerby, Min. Conch. V. p. 85, pi. 
459» fig* 2. Phillips, Geo. York. II. p. 215, pi. 8, fig. 4. 
Transversely elongated; hinge line nearly parallel; umbo 
slightly produced; a little hollow in the middle; surface with 
transverse, prominent, somewhat flexuous, irregular ribs, and 
fine, longitudinal, divergent strife; basal line hollow in the 
middle. 
Mountain Limestone, Castleton, Derbyshire. 
