Orbicula. 
CONCHIFERA. 
143 
4. Orbicula granulata. —The Granulated Orbicula, pi. 
XLIX. fig. 10 and 2G. 
0 . granulata . Sowerby, VI. p. 6, pi. 506, fig. 3, 4. 
Brown's Elements Fossil. Conch, p. 75, pi. 9, fig. 10. 
Nearly orbicular ; conical, patelheform, with a rather 
acute apex, and sides a little rounded; surface with numer¬ 
ous granulated radiating struc, crossed by many lines of growth. 
Great Oolite, Ancliff, Wiltshire. 
5. Orbicula Humpuriesiana. —Ilumphrio’s Orbicula, pi. 
XLIX. fig. 8, 9. 
0. Humphriesiana . Sowerby, VI. p. 5, pi. 506*, fig. 2. 
Conical, orbicular; conical, depressed; apex eccentric, and 
rather obtuso; surface with many divergent striae. 
Kimmeridge Clay, Shotover Hill, Oxfordshire. 
6. Orbicula reflexa. —The Reflexed Orbicula, pi. XLIX. 
fig. 17, 18, 19. 
0 . reflexa . Sowerby, II. p. 4, pi. 50G, fig. 1. Ib. Zool. 
Jour. II. 321. 
Somewhat elliptical ; thin, surface smooth, polished; 
upper valve convex, covering the reflex edge of the lower 
valve; apex eccentric, placed very near to one end, lower 
valve flat, with the vertex nearly central, and a reflexed 
margin in consequence of the disc behind the apex being con- 
cavo ; byssal sinus largo and elongated. 
7. Orbicula latissima. —The very Broad Orbicula, pi. 
XLVIII. fig. 35. Patella latissima , p. 105. 
Patella latissima. Sowerby, II. p. 88, pi. 139, fig. 1 and 5. 
Depressed, smooth, slightly ovate, and very thin; vertex 
eccentric; surface concentrically undulated. 
Oxford Clay, Scarborough and Elberston. 
8. Orbicula nitida. The Shining Orbicula, id. XLIX. 
fig. 10, 21, and 22. 
0. nitida. Phillips, Geo. York. II. p. 221, pi. 11, fig. 
10, 11, 12, 13. 
Slightly ovate ; upper valve conico-lenticular; apex obtuso, 
situato near the narrow end ; surface covored with fine wide- 
set strim, radiating from the apex to the sides. 
Carboniferous Limestone, at Bowes, Pateley Bridge, Leo, 
Ilarolaw, and Otterburn, Coalbrookdale. 
9. Orbicula mutabala. —The Changeable Orbicula, pi. 
XLIX.* fig. 1. 
O. nitida. Portlock, Geo. Rep. p. 446, pi. 32, fig. 14, 
variety. 
Slightly ovate, glabrous, with somewhat irregular and 
faintly defined lines of growth, and extremely fine radiating 
striae, which can only bo seen by the aid of a lens; beak 
remote, distant about one-fourth of tho diameter from the 
margin, its elevation being about one-third of its diameter ; in 
most instances, however, only about a fourth. 
Distinguished from 0. nitida by the nearly obsolete very faint radiat¬ 
ing stria}. 
Carboniferous Strata, in Shale, at Benburb, Ireland. 
10. Orbicula cincta.— -The Girdled Orbicula, pi. XLIX.* 
fig. 9. 
O. cincta. Portlock, Geo. Rep. p. 446, pi. 32, fig. 15. 
Nearly circular, with fine concentric lines of growth; 
apex not a third of the diameter from the margin, and ele¬ 
vated about a third; lower valve also convex, with a truncated 
apex. 
Carboniferous Limestone Shale, Benburb and Tyrone, Ire¬ 
land. 
11. Orbicula ljevigata. —Tho Smooth Orbicula, pi. 
XLIX. fig. 10. 
O. Icemgata. (Munster.)—Portlock, Geo. Rep. p. 445, pi. 
32, fig. 11, 12. 
Circular, highest towards the beak, which is only slightly 
arched, short, and at tho outer margin depressed; shell smooth, 
the lines of growth hardly visible. 
Silurian, gritty coarse Schists, Tyrone, Ireland. 
12. Orbicula oblongata. —Tho Oblong Orbicula, pi. 
XLIX.* fig. 12. 
O. elongata. Portlock, Geo. Rep. p. 445, pi. 32, fig. 13. 
Elongated, greatly flattened, and smooth ; beak slightly 
raised, and situate near tho margin. 
Differs from 0 . lasvigata in the beak not being so close to the margin. 
Silurian, gritty Schists, Tyrone, Ireland. 
13. Orbicula radiata. —The Rayed Orbicula, pi. LXIX.* 
fig. 13. 
O. radiata. Phillips, Geo. York. I. p. 101, pi. 4, fig. 12. 
Slightly ovate ; apex placed near the narrow end ; general 
surface smooth ; with a series of radiating striae round the 
margin. 
Coral Crag, Mai ton, Yorkshire. 
14. Orbicula subrotunda. —Tho llalf-round Orbicula, 
pi. XLIX.* fig. 14. 
O. subrotunda. Portlock, Geo. Rep. p. 445, pi. 32, fig. 10. 
Slightly oval; apex situate one-fourth tho diameter from 
the margin. 
Silurian Schisms, Tyrone, Ireland. 
15. Orbicula Norvegica. —The Norwegian Orbicula, 
pi. XLIX.* fig. 11. 
O. Norvegica. Lamarck, An. San. Vert. VI. pt. I. p. 242. 
Brown’s Illustrations of Recent Conchology of Brit. p. 6, pi. 
20, fig. 21, 22, and pi. 22, fig. 9. 
Form irregular; margin ruggid, upper valve pattelliform, 
a little convex, with concentric lines of growth ; vertex a 
little off the centre; under valve quite flat, adhering its whole 
circumference to other bodies; provided with lour muscular 
impressions. 
Coral Crag, Sutton. 
Tribe 11.—RUDISTA. 
Animal unknown, as are also tho ligament and hinge; shel 
with very unequal valves, and destitute of distinct umbones. 
Genus XIV. IIIPPONYX.— Defrance. 
Generic Character .—Shell bivalve, adherent, inequivalve, 
irregular; muscular impressions in both valves horse-shoe 
shaped; lower valve affixed to marine bodies, orbicular, much 
compressed, and considerably thickened in some instances, 
with its margins always elevated, particularly in front, its 
muscular impression consisting of two contiguous semilunar 
portions, which are distant, broad, and rounded in front, 
nearly confluent and narrow behind; upper valve patellilorm, 
generally subconic, in some instances compressed, with a 
posteriorly submarginal umbo pointing backwards ; muscular 
impressions situate near the posterior margin, with its two 
lobes considerably more remote, and obliquely truncated iu 
