S PH-ERA. 
CONCHIFERA. 
197 
/. triangularis. Beau. Mag. Nat. Ilist. N. Ser. III. p. 
60, fig. 20. 
Triangular, smooth, inflated ; beaks small, considerably in¬ 
flected; surface with pretty strong, concentric lines of growth, 
and fine, somewhat regular, longitudinal stria); basal line 
much arcuated. 
In the Cornbrash, Scarborough, Yorkshire. 
11. Isocardia angulata.— The Augulatcd Isocardia, pi. 
LXXIX. figs. 24, 25. 
7. angulata . Phillips, Geo. York, 1. pi. 2, figs. 20, 21. 
Sub-triangular, beaks obtuse and large; surface smooth ; 
base very little curved, and rather acute at both extremities. 
TheSpecten Clay, Speeton, Yorkshire. 
12. Isocardia rhomdoidalis.— The Rhomboidal Isocardia, 
pi. LXXIX. fig. 16. 
/. rhomboidalis. Phillips, Geo. York, I. pi. 3, fig. 28. 
Rhomboidal, or obliquely quadrate ; anterior side depressed; 
smooth ; posterior side with many narrow concentric furrows ; 
basal lino triangular. 
The Coral Rag, Malton, Yorkshire. 
13. Isocardia axiniformis. —The Axinus-formcd Isocardia, 
pi. LXXX. fig. 6. 
/. axiniformis. Phillips, Geo. York, II. p. 209, pi. 5, f. 13. 
Transversely elongated, wedge-shaped ; beaks rather short 
and involute; surface glabrous, with many fine, concentric 
stria). 
The Carboniferous Limestone, Northumberland. 
14. Isocardia nitida. —The Shining Isocardia, pi. LXXX. 
fig. 17. 
/. nitida . Phillips, Geo. York, I. pi. 9, fig. 10. 
Ileart-shaped ; beaks involute ; surface smooth and shining. 
The Great Oolite, Coughton, Wykc. 
15. Isocardia tumida. —The Tumid Isocardia, pi. LXXIX. 
fig. 15. 
/. tumida . Phillips, Geo. York, I. pi. 4, fig. 25. 
Heart-shaped, much inflated, rather elongated ; beaks tumid, 
considerably involute ; surface with transverse lines of growth, 
and crossed by longitudinal, radiating, shallow furrows, com¬ 
mencing on the disk, and terminating in the basal margin all 
round. 
The Calcareous Grit, Gristhorpc, Yorkshire. 
Genus XVIII.—CARDIOMORPIIA. — Koninck. 
Shell equivalve, inequilateral, frequently oblique, ami trans¬ 
versely elongated ; ventricoso and heart-shaped ; hinge-line 
straight, and extending from behind the beaks, and terminating 
in a produced acute point; hinge destitute of teeth; inside 
with two muscular impressions; the pallial impression simple, 
and destitute of a sinus ; texture of the shell thin. 
1. Cardiomorpha oblonga.— The Oblong Cardiomorpha, 
pi. LXXIX. figs. 30, 31, and pi. LXXXI. lig. 5. 
C. oblong a. Koninck, p. 103, pi. 2, fig. 7. Isocardia ob- 
long a. Sowerby, V. p. 148, pb 491, fig. 2. Phillips, Geo. 
York, II. p. 209, pi. 5, fig. 9. 
Oblong, sub-compressed, anteriorly expanded, and very 
short; with the beaks close to and curved into it; posterior 
side large; hinge-line nearly straight; surface smooth. 
The Carboniferous Limestone, Dublin, Kildare, and Bol- 
land, Yorkshire. 
Genus XIX.—OPIS.— Defranee. 
Shell equivalve, rhomboidal, heart-shaped, inflated; beaks 
involute and approximate, nearly touching ; hinge-area ob¬ 
lique ; hinge with a large striated tooth, fitting into a cavity 
iu the opposite valve; lunette very large, deep, oval, aud 
pointed below the cavity, which has two smaller teeth on 
each side. 
1. Opis lunulata. —The Luuiform Opis, pi. LXXX. 
figs. 15, 16. 
Cardita lunulata. Sowerby, III. p. 55, pi. 232, figs. 1,2. 
Rhomboidal, inflated, and pointed anteriorly, and separated 
by a projecting keel ; beaks involute, considerably produced ; 
posterior side rounded, and with an incurved margin, which 
confines the deeply excavated lunette, and strongly impressed 
by the involute beaks ; anterior side furnished with a series of 
steps, the first of which is somewhat concave, giving the mar¬ 
gin a truncated aspect; right valve with two teeth, and one 
in the left, which looks into a cavity between the two in the 
opposite valve ; surface with trausverse ribs; base acute. 
The Great Oolite, Cain’s Cross, and the Inferior Oolite, 
D undry. 
2. Opis similis. —The Similar Opis, pi. LXXX. fs. 13, 14. 
Cardita shnilis. Sowerby, III. p. 56, pi. 232, fig. 3. 
Phillips, Geo. York, I. pi. 3, fig. 23. 
Gibbose, rhomboidal, anterior side separated by a produced 
serrated keel; lunette nearly heart-shaped, and almost flat; 
beaks involute ; surface transversely ribbed. 
Resembling O. lunulata , but the shell is shorter, more inflated ; the 
ribs less prominent on the sides, and the base not so acute. 
The Coral Rag, Malton and Scarborough, and the Inferior 
Oolite, Dundry. 
Gen us XX.—SPII TER A. — Sowerby. 
Shell bivalve, globular, with short, obtuse, incurved ears ; 
with one central and two (?) remote teeth about the hinge, the 
line of which is lengthened, slightly incurved, and terminating 
at one end with an indistinct tooth, beneath the insertion of 
the ear; in its centre is a largo irregularly-formed tooth, 
transversely depressed, and pointing towards the incurved ap¬ 
proximate beaks. It is a heavy shell, gibbose in its shape. 
1. Spider a corrugata. —The Corrugated Sptuera, pi. 
LXXX. fig. 10. 
S. corrugata. Sowerby, Min. Conch. IY. p. 42, pi. 335, 
fig. 2. Venus Ringmerensis. Mantell, Geo. Sussex, p. 126, 
pi. 25, fig. 5. 
Shell gibbose, ponderous ; surface with coarse corrugations ; 
rugae placed transversely and obtuse, more conspicuous near 
the sides, nearly smooth in the middle, but extending over the 
ears. 
In the Iron Sand Formation, oast of Sandown Bay, Isle of 
Wight; and at Middleham and Ringmer, and the Lower 
Greensand, Sandgate and Shauklin. 
