Plicatula. 
CONCHIFERA. 
151 
straight and obtuse; auricles small, the anterior one longest, 
situated in a large, broad, deep furrow ; surface smooth, with 
obscuro longitudinal divergent stria); and crossed by a few 
hollow lines of growth. 
Inferior Oolite, Glaizdale and Cotswold, and the Lias, 
Weston and Lyme Regis. 
2. Plagiostoma spinosum. —The Spinous Plagiostoma, 
pi. LXVI.* fig. 4. 
P. ipinosa . Sowerby, I. p. 177, pi. 78. Spondylus, Gold- 
fuss, pi. 105, fig. 5. 
Obovate; umbones nearly central and rather blunt; sides 
nearly equal, and not much arched ; one valve flat and the 
other more inflated; surface With numerous flat ribs and deep 
intermediate furrows, which extend to the inside of the valves, 
terminating in regular crenulations on the margins; the 
convex valve provided with irregularly set, somewhat dis¬ 
tant, curved, and long spines, each of which has a dorsal ridge 
and a furrow beneath ; some of those nearest the base of the 
shell are equal to half the length of the valve, whole surface 
covered with very line, raised, transverse stria). 
Upper Chalk, Northfleet, Lewis, Norfolk, and Wiltshire. 
3. Plagiostoma punctatum. —The Punctured Plagios¬ 
toma, pi. LXVI. fig. 10. 
P. punctata . Sovverbv, II. p. 25, pi. 113, figs. 1, 2. Lima. 
Goldfuss, p. 81, pi. 101, fig. 2. 
Obliquely obovate, compressed; anterior side long and 
nearly straight; ears nearly equal; whole surface covered with 
numerous, uoarly regular, longitudinal coarse stria), and very 
fine transverse stria), which produces a somewhat punctated 
appearance. 
Inferior Oolite, Cotswold Hills, Lias, Weston, and Picke- 
ridge Hill. 
4. Plagiostoma elqngatum. —The Elongated Plagios¬ 
toma, pi. LXVI. fig. 4. 
Modiola parallela. Sowerby, I. p. 31, pL 9. Upper right- 
hand figure, Lb. VL p. 113, pi. 559, fig. 2. 
Transversely elougated, nearly twice as broad as long, acutely 
convex, anterior and posterior sides parallel ; beaks rather 
sharp ; lower margin straight, short, and nearly at right angles 
with the sides, which are almost straight and parallel; surface 
with a few transverse furrows. 
The Gualt, Folkstone and Ridge; the Lower Greensand, 
Artherfield Point, Isle of Wight, and Court-at-Street. 
5. Plagiostoma concentric cm. —The Concentric Plagios¬ 
toma, pi. LX VL fig. 2. 
L J . concentrica. Sowerby, VI. p. 113, pi. 559, fig. 1. 
Acicula oval is. Phillips, Goo. York, I. pi. 3, fig. 30 (?) 
Obliquely elliptical, convex, most so towards the beaks, 
hinge-line short and oblique ; surface with numerous longi¬ 
tudinal divergent striae, and a few concentrical lines of growth ; 
beaks slightly produced ; shell thick. 
The Luis, Ethie, Cromarty. 
6. Plagiostoma duplicatum. —The Double-Plaited Pla¬ 
giostoma, pi. LXVI. fig. 6. 
P. duplicata . Sowerby, pi. 559, fig. 3, Phillips, Geo. York, 
I. pi. 0, fig. 2. 
Obliquely oboval, convex ; beaks rather produced ; surface 
with numerous sharp, divergent ribs, with a sharp elevated 
line intervening between each. Tho ribs are about twenty-five 
in number. 
Tho Coral Rag, Malton and Scarborough, the Kelloways 
Rock, Ilackness, and the Lias, Bredon and Weston. 
7. Plagiostoma Hopeei. —Iloper’s Plagiostoma, pi. LXVI. 
fig. 18. 
P. Hoperi. Sowerby, IV. p. 111, pi. 380. 
Transversely and obliquely ovate; convex ; almost smooth ; 
surface with very slender, nearly obsolete, divergent, obscurely 
puntated striio, which are strongest at the sides; anterior side 
straight and a little concave, cars unequal, small, with longi¬ 
tudinal stria). 
The Chalk, Lewis and Norwich, and the Upper Greensand, 
Isle of Wight. 
8. Plagiostoma rusticum. —Tho Rude Plagiostoma, pi. 
LXVI. fig. 1, 
P. rusticum . Sowerby, IV. p. Ill, pi. 381. 
Transversely oblong-ovate, oblique, smooth, convex, hinge¬ 
line very short, ears obscure and very short, the anterior side 
straight, convex along the middle, surface with about twenty- 
five deep, irregular, strong, somewhat waved, divergent, longi¬ 
tudinal furrows; beak a little prominent. 
The Portland Stone, Great Ilazely, Oxfordshire, and the 
Coral Rag, Malton and Shotover. 
9. Plagiostoma laeviusculum. —The Smooth Plagios¬ 
toma, pi. LXVI. fig. 17. 
P. IcBviusculum. Sowerby, IV. p. 112, 382. 
Subtriangular, oblique, its length exceeding its breadth, 
hinge-line oblique, short, and intercepted; ears small, un¬ 
equal, longitudinally furrowed ; anterior side straight, whole 
surface covered with many largo, slightly elevated, longi¬ 
tudinal, divergent ribs, and numerous irregularly elevated 
concentric lines of growth ; margin slightly scolloped. 
The Coral Rag, Malton, Yorkshire. 
10. Plagiostoma rigidum. —The Rigid Plagiostoma, pi. 
LXVI. fig. 5. 
P. riijidum. Sowerby, II. p. 27, pi. 114, fig. 1. 
Inflated, obliquely obovate ; binge-line rather long, and 
considerably oblique, ears narrow and nearly equal; anterior 
side long, straight, and a little coucave; posterior side round¬ 
ed, beaks obtuse, surface with numerous, sharp, irregularly 
undulating thread-like, longitudinal, divergent ribs, with very 
minute, intervening stria*, which cannot be discerned without 
the use of a lens ; beaks rather produced. 
The Lower Greensand, North Wiltshire, and the Coral 
Rag, Malton and Shotover. 
11. Plagiostoma ovale. —The Oval Plagiostoma. pi. 
LXVI. fig. 13. 
P. oval is. Sowerby, II. p. 27, pi. 114, fig. 3. 
Somewhat ventricose, elongated, moderately oblique ; sides 
nearly equal, the anterior one a little concave, and slightly 
recurved, ears rather large ; surface with numerous small 
rounded, equidistant, divergent ribs, and tho intervening 
spaces, with minute, transverse strise. 
The Great Oolite, near Bath. 
12. Plagiostoma obscuuum. —The Obscure Plagiostoma, 
pi. LXVI. fig. 3. 
P. Obscura . Sowerby, II. p. 28, pi. 114, fig. 2. 
