130 MOLLuSCA. Atrypa. 
Plentiful in the Devonian Limestone at Petherwin. 
26. Atrypa indentata. —The Indented Atrypa, pi. LIV. 
fig. 23, 24. 
Atrypa indentata. Sowerby, Geo. Trans. V. 2nd series, pi. 
54, fig. 6. 
Transversely obovate, with an indented base; beak small, and 
produced ; edge of the lower valve elevated. 
Devonian Limestone, Petherwin and Barnstaple, where it is 
very abundant. 
27. Atrypa juvenis. —The Young Atrypa, pi. LIV. fig. 
74, 75. 
Atrypa juvenis. Sowerby, Geo. Trans. V. 2nd series, pi. 56, 
fig. 8. Phillips, Pal. Fos. p. 90, pi. 35, fig. 165. 
Longitudinally ovate, slightly convex, smooth, curved; base 
a little pointed; valves nearly equal, the lower curved upwards, 
with a small beak. 
Devonian Limestone, Plymouth. 
28. Atrypa lachryma —The Tear Atrypa, pi. LIV. fig. 
30, 31. 
Atrypa lachryma. Sowerby, Geo. Trans. V. 2nd series, pi. 
56, fig. 9. 
Longitudinally subglobose, smooth ; beak hardly prominent; 
sides rounded, and nearly equal; base straight, or slightly waved, 
scarcely raised, except at the edge, which is deeply sinuated by 
the projection of the inferior valve; mesial furrow broad, flat, 
and bounded by two sharp ridges. 
Devonian Limestone, Plymouth. 
29. Atrypa striatula. —The Finely-striated Atrypa, pi. 
LIV. fig. 46. 
Atrypa striatula. Sowerby, Geo. Trans. V. 2nd series, pi. 
54, fig. 10. 
Suborbicular, convex; surface with fine, close-set, longitudi¬ 
nal, divergent stria?. 
Devonian Limestone, Petherwin, Barnstaple, and Fowey. 
30. Atrypa plebeia. —The Common Atrypa, pi. LIV. 
fig. 51, 52. 
Atrypa plebeia. Sowerby, Geo. Trans. V. 2nd series, pi. 56, 
fig. 12, 13. Spirifera plebeia , Phillips, Pal. Fos. p. 70, pi. 28, 
fig. 121. 
Transversely obovate, smooth, and but slightly convex; beak 
hardly protruding; base produced, and but little turned up ; 
lower valve with a very slight depression. 
Devonian Limestone, Mount Wise, Plymouth, and Barton. 
31. Atrypa sph/Erica.—T he Spherical Atrypa, pi. LIV.- 
fig. 57, 58. 
Atrypa spluerica. Sowerby, Geo. Trans. V. 2nd series, pi. 
57, fig. 3. 
Ventricose, nearly spherical, slightly wider than long; beak 
small, adpressed; surface with large, longitudinal, rounded ridges, 
and shallow intervening furrows; base deeply sinuated, with five 
elevated ribs. 
Devonian Limestone, Plymouth. 
32. Atrypa hemisph/eiuca.—T he Hemispherical Atrypa, 
pi. LIV. fig. 14, 15. 
Atrypa hemisphcrrica. Sowerby, Sil. Syst. p. 637, pi. 20, 
fig. 7. 
Nearly orbicular, fan-shaped; valves unequal, the one hemis¬ 
pherical, the other almost flat; with a nearly straight back, and 
about twelve angular radii. Length four lines; breadth five lines. 
Lower Silurian Rocks, Ansterdine Hill; Worcestershire; 
Damory Hill, Michaelwood Chace, Gloucestershire. 
33. Atrypa latissima. —The Verv Broad Atrypa, pi. 
LIV. fig. 16, 17. 
Atrypa latissima. Sowerby, Geo. Trans. V. 2nd series, pi. 
56, fig. 25. 
Transversely oblong-ovate; beak short, and nearly straight; 
one valve gradually rounded, the other with the centre of the 
base suddenly reflected, and slightly hollowed, with a corres¬ 
ponding ridge in the other; a series of radiating ribs invest the 
margins of the valves, producing a crenulated edge; upper 
portion of the valves smooth, with a few lines of growth. 
Devonian Shales, Plymouth. 
34. Atrypa globosa —The Globular Atrypa, pi. LIV. 
fig. 25, 26. 
Atrypa globosa. Sowerby, Sil. Syst. p. 637, pi. 22, fig. 2 b. 
Globular, smooth, with obscure channels. Diameter about 
six lines. 
Lower Silurian Rocks, Castell Craig; Gwyddon; and 
Gorllwyn; Caermarthenshire. 
35. Atrypa gibbera —The Gibbous Atrypa, pi. LIV- 
fig. 42, 43. 
Atrypa gibbosa. Portlock, Geo. Rep. p. 460, pi. 38, fig. 1. 
General form nearly orbicular; both valves convex, the ven¬ 
tral one remarkably so, having a haunch-backed aspect, with a 
faint mesial ridge, corresponding to the tongue in the other 
valve; dorsal valve depressed for nearly half its length, from 
whence it suddenly descends, and contracts in the centre into a 
small tongue-shaped process, which protrudes into the ventral 
valve; beaks distant; when viewed through a lens the surface 
presents a finely radiated appearance. 
Carboniferous Limestone, Tyrone, Ireland. 
36. Atrypa decussata —The Decussated Atrypa, pi. 
LIV. fig. 54. 
Atrypa decussata. Sowerby, Geo. Trans. V. 2nd series, pi. 
54, fig. 5. Spirifera decussata , Phillips, Pal. Fos. p. 70, pi. 
28, fig. 120,* 5, c, d. 
Circular; both valves uniformly convex; beaks incurved, ap¬ 
proximate; whole surface with rather sharp, concentric stria?, 
and very fine, equal, interrupted, radiating lines, which give it a 
slightly crenulated appearance. 
In some specimens every third or fourth of the concentric strise are 
Larger than the others. 
Devonian Shales, Brushford; Boggy Point; Pilton; and 
Petherwin. 
37» Atrypa lineata —The Lineated Atrypa, p!. LIV. 
fig. 60, 6i. 
Terebratula lineata. Sowerby, IV. p. 39, pi. 334, fig. 1, 2. 
Spirifera lineata , Phillips, Pal. Fos. p. 70, pi. 28, fig. 120, a. 
Anornites lineatus , Martin, Pet. Derb. pi. 36, fig. 3. 
Transversely oval, gibbose; umbones rather produced, in¬ 
curved, and approaching, the intervening area with an angular 
sinus; whole surface with transverse, rather distant sulci, and 
very minute, close, longitudinal stria*. 
Carboniferous Limestone, Kirby Lonsdale; Castleton, Der¬ 
byshire ; South Petherwin; and Ireland. 
38. Atrypa imbricata. — The Imbricated Atrypa, pi. 
LIV. fig. 66, 67. 
Terebratula imbricata. Sowerby, IV. p. 40, pi. 334, fig. 
3, 4. Spirifer imbricata , Phillips, Geo. York. II. pi. 10, fig. 20. 
