Trigonia. 
OONOHIFERA 
183 
tuse; superior line nearly straight; basal line a little arcu¬ 
ated ; surface with concentric ribs, each of which is bent at a 
right angle in the middle, whore there is a line of largo tu¬ 
bercles extending in an angle from the beaks to the margin. 
The Greensand, Blackdown. 
10. Trigonia spinosa.— The Spinous Trigonia, pl.LXXV. 
fig, 8. 
T. spinosa. Parkinson, Org. Rem. II. pi. 12, fig. 7. 
Sowerby, I. p. 196, pi. 86. Var. Ib. Geo. Trans. 2d Ser. IV. 
p. 196, pi. 13, fig. 3. 
Obliquely ovate; compressed; beaks obtuse; anterior side 
large, and separated from the posterior by an oblique ridge 
extending from the beaks to the margin; on each side of 
which the surface is covered with many divergent spinous ribs, 
bending upwards, and increasing in thickness as they diverge 
from the ridge, and producing a crenulated margin all round. 
The Lower Greensand, Seabrook, Pulborough, Sandgate, 
and Lyme Regis. 
11 . Trigonia spectabilis. —The Notable Trigonia, pi. 
LXXV. fig. 9. 
T. spectabilis. Sowerby, VI. p. 83, pi. 544. 
Sub-ovate, sub-trigonal, convex ; an obtuse, nearly central, 
slightly curved elevation, emanates from the beaks, and ter¬ 
minates on the base ; beaks obtuse, a little turned to one side; 
near to them, three or four smooth, concentric, rounded ribs; 
surface almost smooth, with seven or eight semicircular rows 
of large, blunt, round tubercles, and a few irregular smaller 
ones on the posterior side; both edges rather straight, undu- 
lous, produced by the projecting tubercles; base rounded. 
The Greensand, Blackdown. 
12 . Tiugonia nodosa. —The Nodulous Trigonia, pi. 
LXXV. fig. 10. 
T. nodosa. Sowerby, V. p. 7, pi. 507, fig. 1. 
Somewhat obovate ; beaks obtuse, and nearly central; sur¬ 
face smooth, covered anteriorly with indistinct, irregular rows 
of large, depressed knobs, and some smaller ones on the poste¬ 
rior portion; anterior side rounded, or arcuated; posterior 
side nearly straight from tlie beak for two-thirds the length of 
the valve ; anterior side arcuated ; base rounded. 
The Lower Greensand, Seabrook, Kent. 
13. Trigonia clevellata. —The Club-shaped Trigonia, 
pi. LXXV. fig. 11. 
T. clevellata. Parkinson, Org. Rem. III. p. 175, pi. 12, 
fig. 3. Sowerby, I. p. 197, pi. 87, upper figs. 
Sub-triangular, obliquely elongated, curved ; anterior side 
straight, flattened, with three longitudinal, linear rows of small 
round tubercles; posterior side much arcuated, with from 
twelve to fourteen transverse, curved series of rounded 
tubercles; the surface rather rough ; anterior seam undulous, 
slightly gaping under the curved and small beaks. 
The Lower Greensand, Seabrook, Kent ; the Portland 
Stone, Langcombe and Swindon ; and the Kelloways Rock, 
Weymouth and South Cave. 
14. Trigonia gibbosa. —The Gibbous Trigonia, pi. LXXV. 
fig. 13. 
T. gibbosa. Sowerby, HI. p. 61, pi. 235. 
Sub-triangular, transversely elongated, oblique, and gibbose; 
anterior side nearly straight; posterior side produced, nar¬ 
rowed, and obliquely sub-truncated, with a broad, oblique, 
longitudinal, shallow furrow, or depressions emanating from 
the beak, and terminating on the extreme point of the some¬ 
what beaked terminations; beaks narrow, incurved, and 
approximating; basal line regularly arcuated ; back concave ; 
surface smooth, with transverse, shallow lines of growth, 
which increase in depth and proximity at the base. 
The Lower Greensand, Lockswell Heath. 
15. Trigonia pustdlata.—T he Pustulous Trigonia, pi. 
LXXV. fig. 12. 
T. gibbosa . Var. B., Sowerby, III. p. 61, pi. 236. 
Sub-triangular, gibbose; anterior side rounded; posterior 
side produced, and obliquely sub-truncated; back somewhat 
concave; base considerably arcuated anteriorly, and poste¬ 
riori v a little concave, giving it a beaked aspect; beaks ob¬ 
tuse and incurved; whole surface with shallow concentric 
furrows, the anterior portion with series of irregularly set, 
oval pustules. 
The Portland Stone, Portland; the Vale of Wardour; 
Swindon, and Brill. 
Although the two preceding shells bear a striking similitude in form, 
yet I cannot agree with Sowerby and others that they are the same 
species. 
16. Trigonia cuspidata.—T he Pointed Trigonia, pi. 
LXXV. figs. 14, 15. 
T. cuspidata . Sowerby, VI. p. 8, pi. 507, figs. 4, 5. 
Sub-triangular, compressed ; anterior side rounded; poste¬ 
rior side abruptly truncated, with a projecting tag at its lower 
angle; surface with about seven concentric ribs, which are 
pointed and angular at the posterior division of the valves ; 
beaks acute; teeth of the binge much elongated ; back 
rounded ; basal line arcuated ; texture of the shell thin. 
The Great Oolite, Ancliff, Wiltshire. 
17. Trigonia pulmjs.—T he Bug Trigouia, pi. LXX\ 
figs. 16, 17. 
T. pullus . Sowerby, VI. p. 10, pi. 508, figs. 2, 3. 
Sub-triangular, inflated; anterior side rounded ; posterior 
side obliquely truncated, angular at its lower extremity; beaks 
rather obtuse; anterior portion with numerous transverse* 
smooth ribs, and separated from the other side by a longitudi¬ 
nal, rather thickened, curved, slightly crenated rib, with seve¬ 
ral similar ones on the flattened posterior side ; lunette large 
and transversely striated. 
The Oxford Oolite, Upware, near Cambridge, and the 
Great Oolite, Ancliff, and Cain’s Cross. 
18. Trigonia affixis.—T he Allied Trigonia, pi. LXXVI. 
fig. 41. 
T. affinis- Sowerby, III. p. 11, pi. 208, fig. 3. 
Transversely ovate; anterior side rounded, smooth, and 
covered with transverse, flattened ridges; posterior side a little 
produced, slightly and obliquely sub-truncated, a little beaked 
at its lower angle; basal line nearly straight; beaks very ob¬ 
tuse. 
The Greensand, Blackdown and Parham. 
19. Trigonia eccentrica.—T he Eccentric Trigonia., pi. 
LXXVI. fig. 45. 
T. eccentrica. Parkinson, Org. Rom. III. p. 175, pi. 12, 
fig. 5. Sowerby, III. p. 11, pi. 208, figs, 1, 2. 
Transversely sub-triangular, convex; anterior side short, 
rounded ; posterior side elongated, acuminated, and truncated ; 
its length little more than half its width; beaks obtuse, in- 
