Atrypa. 
MOLLUSCA. 
129 
Pentraedral; sides rounded; depressed; the mesial furrow in 
both valves flattened; surface covered with broad, undulating 
fringes, the external or marginal one very greatly expanded. 
Mountain Limestone, Holland. 
13. Atrypa fimbriata* —The Fringed Atrypa, pi. LIV. 
fig. 72, 73. 
Atrypa Jimbriata. Sowerby, Min. Conch. VII. p. 16, pi. 
617, fig. 4. Spirifera Jimbriata , Phillips, Geo. York. II. p. 
220. See also p. 112. 
Transversely subovate, subcompressed; centre of each valve 
somewhat longitudinally depressed; surface uneven, with im¬ 
bricated and striated fringes. 
Mountain Limestone, Kendal, Westmorland. 
14. Atrypa protracta. —The Continued Atrypa, pi. 
LIV. fig. 55, 56. 
Atrypa protracta. Sowerby, Geo. Trans. V. 2nd series, pi. 
56, fig. 16. 
Transverse, triangular; lateral angles rounded; beak pro¬ 
duced, and acute; sides flattened; seam undulating; base 
elevated, with about four plaits, its sides smooth. 
Devonian Limestone, Plymouth. 
15. Atrypa oblonga. —The Oblong Atrypa, pi. LIV. 
fig. 47, 48. 
Atrypa oblonga . Sowerby, Min. Conch. VII. p. 16, pi. 617, 
fig. 3. 
Oblong-oval, very convex; base hollowed; beak small, 
pointed, and incurved ; sides obtuse; centre of each valve with 
a plain, shallow, mesial furrow. 
There are some slight indications of its being fimbriated. 
Mountain Limestone, Queen’s County, Ireland. 
16. Atrypa crenulata. —The Crcnulated Atrypa, pi. 
LIV. fig. 34, 35. 
Atrypa crenulata. Sowerby, Geo. Trans. V. 2nd series, pi. 
56, fig. 17. Phillips, Pal. Fos. p. 85, pi. 34, fig. 152. 
Pentagonal, compressed ; surface smooth; beak very small; 
base broadly and suddenly elevated; with numerous, small, 
lengthened crenulations near the margins; sides smooth. 
Devonian Limestone, Barton and Plymouth, Devonshire. 
17. Atrypa pectinifera —The Comb-like Atrypa, pi. 
LIV* fig. 3, 4. 
Atrypa pectinifera. Sowerby, Min. Conch. VII. p. 14, pi. 
616. 
Transversely obovate, equally convex, subcompressed; beak 
small; surface covered with concentric, ciliated fringes; the 
external one with a rather lengthened fringe. 
Plentiful in the Magnesian Limestone, Humbleton Ilill, near 
Sunderland. 
18. Atrypa desquamata. —The Peeled Atrypa, pi. LVI.* 
fig. 1, 2, 3, 4. 
Atrypa desquamata. Sowerby, Geo. Trans. V. 2nd series, pi. 
56, fig. 19, 20, 21,22. Phillips, Pal. Fos. p. 82, pi. 33, fig. 146. 
Oblong, gibbous; base obtuse, gently and broadly raised at 
the edge, without elevating the surface; smaller valve deeper 
than the other; surface deeply striated longitudinally, increasing 
in number towards the margin; internal surface striated, or 
punctated. 
This shell is liable to considc*rable variety in size, convexity, and 
coarseness of striae. In the young condition specimens arc found nearly 
globular, while others are lenticular and compressed. 
Devonian Shales, Devonshire and Cornwall. 
A variety of this species is called by Sowerby Atrypa desrptmata com- 
pressa , fig. 21, 22. It is suborbicular, compressed, the valves equal, 
with nearly rectangular sides. 
19. Atrypa fallax. —The False Atrypa, pi. LIV. fig. 18. 
Atrypa falla.v. Sowerby, Geo. Trans. V. 2nd scries, pi. 54, 
fig. 15. Terebralula pleurodon , Phillips, Geo. Y r ork. II. p. 
222, pi. 12, fig. 25, 26. 
1 ransversely ovate; rather inflated, with many strong, ele¬ 
vated, sharp ribs, and deep intervening furrows, producing a 
strongly crenulatcd margin. 
Devonian Shale at Petherwin and Barnstaple. 
20. Atrypa hispida —The Bristly Atrypa, pi. LIV. fig. 1. 
Atrypa hispida. Sowerby, Geo. Trans. V. 2nd series, pi. 
54, fig. 4. 
Transversely oval, compressed; beak but slightly produced; 
surface with concentric fringes of spines. 
Devonian Limestone, Petherwin. 
21. Atrypa impleta —The Filled-up Atrypa, pi. LIV. 
fig. 32, 33. 
Atrypa impleta. Sowerby, Geo. Trans. V. 2nd series, pi. 
57, fig. 2. 
Transversely elongated, its width considerably more than its 
length, ventricose; sides rounded; beaks slightly produced; 
base elevated, with six furrows; whole surface with radiating 
flattened ribs and shallow furrows. 
Devonian Limestone at Plymouth. 
22. Atrypa implexa, —The Plaited Atrypa, pi. LIV. fig. 
83, 84. 
Atrypa implexa . Sowerby, Geo. Trans. V. 2nd series, pi. 
57, fig. 4. 
Transversely obovate; base straight, flat; margin of the base 
and sides broad; surface with numerous, acute plaits, producing 
a toothed margin, with the edges of the valves deeply locked 
into each other. 
Devonian Limestone, Plymouth. 
23. Atrypa triloba —The Three-lobed Atrypa, pi. LIV. 
fig. 27. 
Atrypa triloba. Sowerby, Geo. Trans. V. 2nd series, pi. 
56, fig. 14. 
Tetrahedral, with rounded angles, three lobed; upper valve 
much inflated; lower one nearly flat; base much elevated, with 
about twelve plaits, its sides smooth; lateral lobes reflexed, and 
obscurely plaited; whole surface with broad, flat, radiating ribs, 
and shallow intervening furrows. 
Devonian Limestone, Plymouth. 
24. Atrypa triangularis. —The Triangular Atrypa, pi. 
LIV* fig. 9. 
Atrypa triangularis. Sowerby, Geo. Trans. V. 2nd series, 
pi. 54, fig. 9- 
Triangular; base with two folds; beaks hardly produced 
beyond the circumference of the valves. 
Ferruginous Soft Devonian Limestone, Plymouth. 
25. Atrypa subdentata _The Half-toothed Atrypa, pi. 
LIV; fig. 36, 37. 
Atrypa subdentata. Sowerby, Geo. Trans. V. 2nd series, 
pi. 54, fig. 7. Terebralula subdentata , Phillips, Pal. Fos. p. 
90, pi. 35, fig. 164. Terebratula rotunda, Munster, Beit. 3, 
pi. 14, fig. 15. 
Orbicular, somewhat longer than wide, a little convex, smooth; 
beak very small, but prominent; base three-plaited, and raised. 
2 K 
