18S 
CONCHIFERA. 
PjSCTUNCULUS. 
N. nuda . Phillips, Geo. York, I. pi. 5, fig. 5. 
Transversely elongated ; anterior side short; posterior side 
elongated ; beaks obtuse; surface smooth ; base a very little 
curved. 
Oxford Clay, Scarborough. 
.50. Nucula l.evirostra. —The Smooth-beaked Nucula, 
pi. LXXVI. fig. 71. 
N. Icevirostrum. Portlock, Geo. Sur. p. 439, pi. 36, f. 12. 
Oblong-ovate, club-shaped ; anterior side short and rounded; 
posterior side lengthened and obtuse; beaks obtuse; surface 
with fine concentric strim. 
The Carboniferous Limestone, Tyrone and Armagh, Ireland. 
51. Nucula latissima. —The Very-broad Nucula, pi. 
LXXVI. fig. 73. 
N. latissima . Phillips, Pal. Fos. p. 137, pi. 58, fig. 65.* 
Oblong-ovate ; both extremities almost equally round, with 
a slightly produced angle superiorly. 
The Devonian Shales at Pelton. 
52. Nucula pvgmasa. —The Pigmy Nucula, pi. LXXVI. 
figs. 66, 67. 
N.pygmoia . Goldfuss, pi. 125, fig. 17. N. gibhosa . Forbes, 
Wern. Tr. VIII. pi. 2, fig. 10, 10.* (?) 
Sub triangular; anterior side a little pointed; posterior side 
slightly rounded ; base much arcuated ; beaks obtuse ; surface 
smooth. 
The Pleistoccno Marine Formations, Greenock Railway, 
and the Coral Crag, Ramshot and Sutton. 
53. Nucula plicata. —The Plicated Nucula, pi. LXXVI. 
fig. 62. 
N. plicata. Phillips, Pal. Fos. p. 38, pi. 18, fig. 63. 
Obliquely ovate, compressed; beaks prominent; surface 
smooth, shining, concentrically striated, with the posterior area 
finely plicated. 
The Devonian Shales, Doggy Point. 
54. Nucula radiata. —The Rayed Nucula, pi. LXXVI. 
fig. 65. 
A r . (?) radiata. Portlock, Geo. Rep. p. 430, pi. 36, fig. 11. 
Transversely elongated; anterior side rounded ; posterior 
side acute, and obliquely truncated, and with a ridge emanat¬ 
ing from the beak, and terminating on the side; the flattened 
space with radiating thread-like striie ; beaks well defined. 
The Silurian Rocks, Tyrone, Ireland. 
55. Nucula minuta. —The Minute Nucula. 
N. minuta. Drown, Rcc. Conch. Drit. p. 84, pi. 33, fig. 18. 
Transversely elongated ; anterior side rounded ; posterior 
side produced, acuminated, sub-truncated, and a little curved 
upwards ; surface with strong, transverse striae. 
The Pleistocene Marine Formation, Dalmuir, and the Red 
Crag, Sutton. 
56. Nucula nucleus. —The Kernal Nucula. 
N. margaritacea. Brown, Rec. Conch. Drit. p. 85, pi. 33, 
fig. 12. 
Ovate ; both sides rounded ; beaks near the anterior sido ; 
surface with numerous fine lines of growth. 
The Pleistocene Marine Formations, Ayr, and the Red 
Crag, Sutton. 
57. Nucula rostrata. —The Beaked Nucula. 
V. rostrata. Drown, Rec. Conch. Brit. p. 84, pi. 33, f. 16. 
Transversely elongated ; anterior sido rounded ; posterior 
sido produced and curved upwards, and transversely striated; 
surface slightly ribbed longitudinally, and obliquely crossod by 
the stri&\ 
The Pleistocene Marine Formations, Sutton, &c. 
58. Nucula tenuis. —The Thin Nucula. 
N. tenuis. Drown, Rec. Conch. Drit. p. 85, pi. 33, fig. 13. 
Obliquely ovate ; both sides rounded ; surface smooth and 
shining. 
Pleistocene Marine Formation, Dalmuir and Paisley ; the 
Mammiferous Crag, South wold, and the Red Crag, Bawdsey. 
59. Nucula oblongoides. —The Oblong Nucula, pi. 
LXXVI. figs. 84, 85. 
Wood, Mag. Nat. Ilist. 1840, p. 297, pi. 14, fig. 4. 
Transversely ovate, lanceolate ; somewhat inequilateral, the 
anterior side rounded; posterior side acuminated ; lunule lan¬ 
ceolate ; surface smooth. 
Mammiferous Crag, Bramerton, and the Red Crag, Butlov. 
60. Nucula semi-striata. —The Iialf-striated Nucula, pi. 
LXXVI. figs. 86, 87. 
N. semi-striata. Wood, Mag. Nat. Ilist. 1840, p. 297, pi. 
14, fig. 5. 
Transversely ovate ; somewhat inequilateral ; anterior side 
rounded and smooth; posterior side acuminated, and trans¬ 
versely striated ; substance of the shell thin. 
The Coral Crag, Sutton. 
61 . Nucula trigonula. —TlieTrigonal Nucula,pi. LXXVI. 
figs. 88, 89. 
N. trigonula. Wood, Mag. Nat. Ilist. 1840, p. 295, pi. 
14, fig. 3. 
Obliquely ovate, deltoidal, tumid; beaks prominent; lunuD 
embedded ; convex in the middle ; surface smooth ; internal 
margin crenulated ; longitudinal diameter three sixteenths, 
transverse diameter a quarter of an inch. 
The Coralline Crag, Sutton. 
Genus VIII.—PLEURODON.— >9. Wood. 
Shell bivalve, inequilateral; hinge-lino curved ; several 
uniform, converging, cardinal teeth placed in a row, immedi¬ 
ately under the umbo ; one large lateral tooth, situate poste¬ 
riorly ; ligament external. 
1. Pleurodon ovalis. —PI. LX I.*** figs. 24, 25. 
P. oralis. Wood, Mag. Nat. Ilist. 1840, p. 230, pi. 13, fig. 
1 . Nucula miliaris (?) Dcshayes, Foss, des Env. de Paris, 
pi. 36, figs. 7, 8, 9. 
Ovate, deltoidal, gibbose, sub-orbicular; smooth, margin en¬ 
tire ; hinge with five or six converging cardinal teeth, and a 
large lateral tooth in each anterior side of the valves ; largest 
diameter three thirty-seconds of an inch. 
Genus IX.—PECTUNCULUS.— Lamarck. 
Shell orbicular, sub-equilateral, with the valves close; urn- 
bones near to each other, and separated by a narrow facet or 
area ; hinge semicircular ; teeth numerous, arcuated, oblique, 
