218 
CONCH IFERA. 
Psammoma. 
Genus X LIII.—ARCOPAGI A.— Leach. 
Shell thick, transverse, slightly inequivalve, inequilateral; 
right valve sub-depressed ; beaks very small, nearly straight; 
with two primary teeth in both valves, each of the larger ones 
cleft: loft valve with two remote, lateral teeth, that on the 
anterior side large, with a sinus betwixt it and the margin, 
for the reception of the lateral tooth of the opposite valve, 
muscular impressions large and deep; pallia! impression 
interrupted by a broad, very large, tongue-shaped, oblique, 
nearly central sinus,reaching two-thirds across the valves, both 
defined by a broad, deep, irregular groove; which passes 
through the muscular impressions; margin very broad and 
glossy, as far as thepallial impressions; ligament sub-external, 
near the centre punctated. 
1. Aucopagia crassa —Thick Arcopagia, pi. LXXXIX. 
fig. 39. 
TeUina crassa. Turton, Brit. Bia, p. 109, pi. 7, f. 2, Arco¬ 
pagia crassa , Brown, 111. Rec. Conch. Brit. p. 99, pi. 40, f. 8 
Transversely sub-ovate, somewhat obliquo and twisted, and 
slightly unequal valved, the left ono being the longer, and 
considerably moro convex than the other ; beaks short and 
rather obtuse, and sub-central; whole surface with pretty 
regular, strong, concentric stria?, which become wider as 
they approach the base, with irregular lines of growth ; from 
the beaks a well-marked furrow emanates, and terminates on 
the margin. 
Mammiferous Crag, Postwick, and the Red Crag, Sutton. 
Suu-di vision 111.—SOLEN AIRES. 
G enus XLIV.—PSAM MOBI A.— Lamarck . 
Shell transverse, oblong, somewhat angular, gaping at each 
extremity, and covered with a thin horny epidorinis; with two 
short, bifid, cardinal teeth, in the left valve, and one in the 
right; two distant, sub*orbicular, muscular impressions in both 
valves, situate near each end of the valve; pallial impressions 
with a very large sinus; ligament external, and supported 
upon a prominent fulcrum. 
1. Psammobia RIGIDIA. —The Rigid Psammobia, pi. 
LXXXI1I. fig. 10, and pi. LXXXIX. fig. 48. 
1 J . rigida. Sowerby, Sil. Syst. pt. II. p. 017, pi. 8, fig. 3. 
Considerably elongated transversely, its length not half its 
width; anterior sido somewhat attenuated; posterior side 
truncated; beaks obtuse, situate nearest the anterior side; 
base straight; surface with from ten to twelve sharp trans¬ 
verse ribs and furrows; and three divergent ridges emanating 
from the beaks and passing towards the base. 
The Lower Ludlow Rock, near Aymestrv. 
2. Psammobia Ferroensis. —The Fer.o Psammobia, pi. 
LXXXIX. fig. 44. 
P. Ferroensis . Brown, Ill. Rec. Conch. Brit. p. 101, pi. 
40, figs. 1, 2. 
Transversely elongated, compressed ; anterior side obliquely 
truncated, and with an elevated ridge running from the beaks 
to the base ; posteriorly a little contracted and rounded ; sur¬ 
face with strong transverse stria?, which are angulated on the 
truncations. 
The Coral Rag, Sutton. 
3. Psammobia vespertina. —The Bat’s-wing Psammobia, 
pi. LXXXIX. fig. 54. 
P. vespertina . Brown, Ill. Rec. Conch. Brit. p. 102, pi. 
29, figs. 30, 31. 
Transversely oblong ovate, both sides rounded ; beaks small, 
nearly central ; surface with fine concentric stria?. 
The Coral Crag, Ramshot. 
4. Psammobia solida. — The Solid Psammobia, pi. 
LXXXIX. fig. 47. 
P. solida. Sowerby, IV. p. 55, pi. 342. 
Transversely elongated, compressed, slightly twisted ; ante¬ 
rior side obliquely truncated, with a ridge running from the 
beaks to the margins, and forming a point; surface smooth. 
The Upper Marine Formation, Ileadon Kill. 
5. Psammobia tellinoides.—T he Tellina-like Psammo¬ 
bia, pi. LXXXIX. fig. 49. 
P. tellinoides . Sowerby, Goo. Tr. 2d Ser. IV. p. 1 ?0, pi. 
21, fig. 6. 
Oblong ovate ; anteriorly slightly rounded, with a few short 
longitudinal stria? ; the rest of the shell smooth; posterior side 
rounded; beaks nearly central. 
The Wcalden, Pomiesfiold, Sussex. 
O. Psammobia gracilis.—T he Slender Psammobia, pi. 
LXXXIX. fig. 45. 
P. gracilis. Sowerby, Geo. Tr. 2d Ser. IV. p. 341, pi. 1G, 
fig. 12. 
Transversely elongated, the breadth double the length, near¬ 
ly cylindrical; anterior side obliquely truncated, with an acute 
point below; surfaco with many transverse stria?, which are 
elevated at their extremities, and abruptly angular on the 
truncations. 
The Greensand, Blackdown. 
7. Psammobia Scopula.—T he Scopula’s Psammobia, pi. 
LXXXIX. fig. 50. 
P. Scopula. Turton, Brit. Biv. p. 98, pi. G, fig. 5. 
Transversely oblong ; kidney-shaped; beaks nearly cen ¬ 
tral; sides equally rounded ; anterior side striated in two direc¬ 
tions ; the rest of the surface smooth. 
The Coral Crag, Sutton. 
8. Psammobia Florida.—T he Florid Psammobia, pi. 
LXXXIX fig. 53. 
P.Jlorida. Turton, Brit. Biv. p. 8G, pi. G, fig. 9. 
Transversely oblong oval; beaks nearly central; both sides 
almost equally rounded; surface with closo-set, concentric 
stria?, and minute longitudinal ones. 
The Coral Crag, Sutton. 
9. Psammobia l.evigata.—T he Smooth Psammobia, pi. 
LXXXIX. fig. 52. 
P. Iceviata. Phillips, Geo. York, I. pi. 4, fig. 5. 
Transversely elongated ; obliquely truncated anteriorly, and 
rounded posteriorly ; beaks small, sub-central; surface smooth. 
The Great Oolite, Cloughton and Scarborough ; and the 
Inferior Oolite, Blue Wick. 
