192 
CONOHIFERA. 
ClICU LL/E A. 
Transversely elongated, cylindrical and convex ; anteriorly 
rounded ; obliquely truncated posteriorly ; teeth nearly in a 
straight line. 
The Silurian Rocks, Tyrone, Ireland. 
21. Ahca Nox.—Noah’s Area. 
A. Nocc. Brown, Recent Conch. Brit. p. 8, pi. 33, figs. 
1, 2, 3. 
Transversely oblong, sub-rhoraboidal ; ligamentary area 
wide; beaks remote at their points, and rather prominent; 
surface decussated with fine longitudinal and transverse stria?; 
base with a central hiatus between the valves. 
The Coral Crag, Sutton. 
22. A rca sub-truncata.—T he sub-truncated Area. 
A. sub-truncata. Portlock, Geo. Sur. p. 427, ph 34, fig. 1. 
Transversely ovate, convex; beaks nearly central, slightly 
produced ; hinge-line a little curved; anterior side obliquely 
sub-truncated; base a little rounded. 
The Silurian Rocks, Tyrone, Ireland. 
23. A rca regularis.—T he Regular Area. 
A. regularis. Portlock, Geo. Rep. p. 427, ph 34, fig. 2. 
Almost semicircular transversely; hinge-lino nearly straight; 
teeth slightly circular ; beaks central ; sides rounded ; surface 
smooth. 
The Silurian Rocks, Tyrone, Ireland. 
24. A rca pjsbimilis.—T he Dissimilar Area. 
A. dissimilis . Portlock, Geo. Rep. p. 428, ph 34, fig. 5. 
Obliquely oval, convex; anterior side narrow ; posterior 
side broad ; slightly truncated obliquely ; hinge-line straight, 
with the teeth oblique to the line ; those behind the beaks 
in a line a little curved ; those in front few ; beaks very 
obtuse. 
The Silurian Rocks, Tyrone, Ireland. 
25. Arca obliqua.—T he Oblique Area. 
A. obliqua . Portlock, Geo. Sur. p. 429, ph 34, fig. 6. 
Obliquely transverse ; ovate ; anteriorly short and rounded, 
with an oblique sub-truncation behind ; beaks placed very 
near the posterior side ; teeth slightly oblique to the hinge-line. 
The Silurian Rocks, Tyrone, Ireland. 
26. Arca lactanea.—T he Whitish Area. 
A. lactanea. Wood, Mag. Nat. Hist. 1840, p. 232, ph 
13, fig. 3. 
Transversely oblong-ovate ; beaks approximate ; surface 
with fine longitudinal stria?, decussated with numerous strong 
lines of growth ; internal margin destitute of crenulations; 
cardinal teeth vertical, becoming gradually inclined towards 
the extremities of the hinge-line. 
In the Red Crag, Walton, and the Coral Crag, Sutton. 
27. Arca raridentata.—T he Few-toothed Arca. 
A. raridentata. Wood, Mag. Nat. Ilist. 1840, p. 232, ph 
13, fig. 4. 
Rhomboidal, rather tumid ; anterior side short and rounded ; 
posterior larger, obliquely sub-truncated abovo, and round¬ 
ed below ; the basal line undulous ; beaks large, obtuse ; teeth 
much inclined externally, and with a plain space on the car¬ 
dinal area below the beaks—three on the shorter side set at 
an angle of 45° with the hinge-line, and three nearly hori¬ 
zontal ones on the longer side; surface with fine, longitudinal 
striae, decussated by elevated lines of growth. 
In the Coral Crag, Sutton. 
Genus XII.—CUCULL.EA.— Lamarck . 
Shell sub-equivalve, trapeziform, or sub-quadrate ; ex¬ 
tremely ventricose ; beaks distant, separated by a flat area, 
on which the external ligament is placed; two muscular 
impressions in each valve; the anterior ono is elevated into 
a sharp-edged plate or ledge, projecting from the side of the 
shell; posterior muscular impression flat and indistinct; hinge 
rectilinear, with a series of angular, somewhat irregular teeth, 
set in a straight line, very small near the utnbones, larger and 
more oblique towards both extremities; outside covered by an 
epidermis. 
1. CucuiX/EA antiqua. —The Ancieut Cuculkea, pi. 
LXXVIII. figs. 8, 9. 
C. antiqua. Murchison, Silur. Syst. pt. II. p. 602, pi. 3, 
fius. 1 b and 12 a. 
Shell transversely ovate, smooth, rather convex ; posterior 
side larger than the anterior, and acutely angular; internal 
lamina longitudinal; umbones rather obtuse ; length about 
three-eighths to half an inch; breadth from half an inch to 
three-quarters. 
Found in the lowest beds of the Old Red Sandstone, at 
Iloreb Chapel, Felindre-on-the-Teme, Wales. 
2. Cue ul lx A ovata. —The Ovate Cucullma, pi. LXXVIII. 
fig. 4. 
C. ovata. Murchison, Silur. Syst. pt. II. p. 602, pi. 3, 
fig. 12 b . 
Shell transversely ovate, and nearly convex; uinbones 
placed near the anterior side; interior lamina longitudinal; 
both sides gradually roundod ; length one inch and an eighth ; 
breadth one inch and a-half. 
Found iu the lowest beds of the Old Red Sandstone, at 
Iloreb Chapel, Wales. 
3. Cucull.ea Cawdori. — Cawdor’s Cuculliea, pi. 
LXXVIII. fig. 15. 
C . Cawdori . Murchison, Silur. Syst. pt. II. p. 602, pi. 3, 
fig. 11. 
Shell transversely oval, convex, nearly smooth ; anterior 
side rounded; posterior side obliquely truncated; umbones 
rather acute and nearly central, from whence a rounded ridge 
extends to the posterior angle of the margin, with oblique in¬ 
ternal lamina?. 
Found in Upper Silurian Rocks at Freshwater East, Pem¬ 
brokeshire. 
4. Cccullxa glabra. —The Smooth Cuculla?a, pi. 
LXXVIII. figs. 1, 2. 
C. glabra. Sowerby, I. p. 151, pi. 57. 
Rhomboidal, slightly vontricose, its width about a fourth 
more than its longth ; anterior angle obtuso; posterior edge 
of the front rounded ; hinge area with four divergent furrows ; 
beaks somewhat incurved; whole surface with fine longi¬ 
tudinal stria?, which arc decussated by numorous lines of 
growth ; hinge-line finely striated ; teeth deeply striated. 
Upper Greensand, Warminster and Limo; the Lower 
Greensand, Petersfield. 
5. Cucullxa car i NAT A. —The Iveoled Cuculhea, ph 
LXXVII. fig. 41. 
C. carinata. Sowerby, III. p. 9, pi. 207, fig. 1. 
