PLATE LTV. 
1 . Atrypa Hispida. (Bristly Atrypa.) Transversely oval, compressed; beak produced; with concentric fringes of spines. 
2,3. Leptaena Transversalis. (Transverse Leptcena.) Semi-circular, convex; lesser valve concave; hinge iuflected, with parallel lines ; 
with longitudinal ribs and intermediate striae. Length, £ in.; breadth, j| in. 
4,5. A. Cuboides. (Slightly-cubular Atrypa.) Sub-globose, base elevated; margin, with deep sinus ; beak small, acute; lower valve small, 
with large, produced appendage; with many, narrow ribs. 
6,7. L. Minima. (Least Leptcena.) Semi-circular; hinge-line parallel, inflated; with many, radiating ribs; sides prolonged, auriform. 
Length, J in.; breadth, J in. 
8 . L. Fimbriata. (Fringed Leptcena.) Oblong, hemispherical; umbo large, produced; with six to eight, transverse, crenated sulci; lesser 
valve concave. 
9. L. Fraguria. ( Rough Leptcena.) Hemispherical, with sides produced; beak of convex valve sub-acute; with concentric undulations, 
pustulated. 
10. 11. L. Anomala. (Anomalous Leptcena.) Elongated, triangular; hinge-area long, large, triangular, acute ; beak produced, with spinous 
sides and longitudinal strife. 
12 . L. Complanata. (Even Leptcena.) Semi-ovate, compressed; hinge-line arcuated ; beak produced; with many, linear strife, crossed by 
undulating lines of growth ; base deflected. Length and breadth, 1 in. 
13. L. Duplicata. (Doable-plaited Leptcena.) Semi-circular, transversely elongated, convex; with longitudinal sulci internally. Length 
£ in.; width, 3 in. 
14. 15. A. Hemisphserica. (Hemispherical Atrypa.) Orbicular, fan-shaped; valves unequal; one hemispherical, the other flat; with 
straight back and about twelve, angular radii. Length and breadth, $ in. 
16, 17. A. Latissima. (Very Broad Atrypa.) Transversely obiong-ovate; beak short, straight; one valve rounded, the other with centre of 
base reflected; with a series of radiating ribs on margins of valves ; with a few lines of growth. 
16*. L. Ambigua. (Ambiguous Leptcena.) Compressed; hinge-line parallel; beaks produced; deeper valve concentrically angulated; with 
Btrong, longitudinal stria:*, crossed by flextious, rounded ribs. 
18. A. Fallax. (False Atrypa.) Transversely ovate, inflated; with many, strong ribs and deep sulci; with crenulated margin. 
19, 20. L. Lata. (Broad Leptcena.) Semi-circular; base straight; upper valve convex; lower valve concave; with radiating ridges; hinge¬ 
line parallel; with eight to ten, simple, acute spines. 
21,22. A. Ling*uifera. (Tongue-shaped Atrypa.) Orbicular; convex, smooth ; beaks large ; base tongue-shaped. Length, £ in. 
23, 24. A. Indentata. (Indented Atrypa.) Transversely obovate, with indented base; beak small, produced. 
25, 26. A. Globosa. (Globular Atrypa.) Globular, smooth, with obscure channels. Diameter, i in. 
27. A. Triloba. (Three-lobetl Atrypa.) Tetrahedral, three-lobed; upper valve inflated; lower one flat; base, with about twelve plaits* 
lateral lobes reflexed, plaited ; with radiating ribs and shallow 6 ulci. * 
28, 29. A. Orbicularis. (Orbicular Atrypa.) Sub-orbicular ; valves equal, with small sinus in base and many, forked sulci. Length l in • 
breadth, 5 in. 2 *' 
30,31. A. Lachryma. (Tear AtrypaA Longitudinally sub-globose, smooth; sides rounded; base straight; base sinuated by projection of 
inferior valve; mesial sulcus broad, flat, witfi two, sharp ridges. 
32, 33. A. Impleta. (Filled-up Atrypa.) Transversely elongated, ventricose; sides rounded ; beaks produced ; base elevated with six sulci • 
with radiating, flattened ribs and shallow sulci. 
34,35. A. Crenulata. (Crenulated Atrypa.) Pentagonal, compressed, smooth; beak minute; base elevated; with many crenulations near 
margins. 
36,37. A. Subdentata. (Half-toothed Atrypa.) Orbicular, convex, smooth; beak minute, but prominent; base three-plaited, raised. 
36*. L. Rugosa. (Rugged Leptcena.) Semi-circular; hinge-line, with two, auriform processes; lower valve convex ; with regular, concentric 
wrinkles ; border, with rounded undulations, crossed by many, filiform strife. Length, 1 in. 
38, 39. A. Crassa. (Thick Atrypa.) Spherical, smooth, thick; with three, deep, muscular impressions, central one liuguiform, striated • 
lateral ones with five or six sulci. ’ 
40,41. A. Obovata. ( Obovate Atrypa.) Transversely obovate, convex, smooth; beaks small, contiguous ; base, with marginal elevation in 
one valve, forming rounded sinus in edge of other. Length and breadth, £ in. 
42, 43. A. Gibbosa. (Gibbous Atrypa.) Orbicular; both valves convex; ventral one especially so, having hunch-backed aspect; dorsal ono 
with small, linguiform processes in centre; beaks distant. 
44, 45. A. Compressa. (Compressed Atrypa.) Transverse, ovate, compressed, smooth ; beaks small; sides rounded. Length and breadth 4 in 
46. A. StriatUla. (Finely-striated Atrypa.) Sub-orbicular, convex; with tine, longitudinal, divergent stria*. * 2 
47, 48, 59. A. Oblonga. (Oblong Atrypa.) Oblong-oval, convex; base hollowed; beak small, incurved ; sides obtuse; centre of each v air 
with shallow, mesial furrow. “ 1VC 
49, 50. A. Aspera. (Rough Atrypa.) Orbicular; valves convex ; base truncated; with many, radiating sulci, crossed by undulating buninm 
Diameter, J in. n 
51, 52. A. Plebeia. (Common Atrypa.) Transversely obovate, smooth, convex ; beak hardly protruding; base produced. 
63. A. Cassidea. (Little Helmet Atrypa.) Oblong-ovate, ventricose, smooth; beak large; sides and base rounded; with a few linna 
growth on each valve. 01 
j. 54. A. Decussata. (Decussated Atrypa.) Circular; valves convex ; beaks incurved, approximate ; with sharp, concentric strife and radiating 
50, 56. A. Protracta. (Continued Atrypa.) Trausverse, triangular; beak produced, acute; sides flattened; seam undulating* bisn 
about four plaits. 0 » wun 
57, 58. A. Sphaepica. (Spherical Atrypa.) Ventricose, spherical; beak small, adpressed ; with large, longitudinal ridges, and shallow e„i A : . 
base smuated, with live ribs. BUIC1 » 
60, 61. A. Lineata. (Lineated Atrypa.) Transversely oval, gibbose; umbones produced, incurved; with transverse sulci, and 
longitudinal stria). * minute, 
02 , 63. L. Longispina. ( Long-spined Leptcena.) Semi-circular ; hinge-line, with large auricular processes; convex valve,with mesial furrnw • 
smaller valvo concave; one long, horizontal spine and several smaller ones near each side of convex valve. ’ 
and breadth abmU^ii^* ( Rounded Atrypa.) Orbicular, convex, smooth; beaks small, equal; with fine, longitudinal sulci towards base. Length 
laminro ^vitl^io^ngTu l^ a ^ a ^ 1 (Imbricated Atrypa.) Transversely oval, gibbose; beaks produced, iucurved; hingo-liue short; with about twelve 
t *1?’ A 9 Lens. (Lens-formed Atrypa.) Sub-orbicular, compressed, smooth, with obscure radiations ; upper valve elevated in #*nr 
Length, 2J in. ; breadth, 2 in. 1,1 cemre - 
70, 71. A. Expansa. (Expanded Atrypa.) Transversely sub ovate, inflated; base straight; without mesial fold; with striated imhrw»o*«a 
fringes; beak small, produced, incurved. ’ 1Iuullc “tea 
imbricated .^rif/T^ring^^* ^ Frin ^ ed ^ tri JP a ‘) Transversely sub-ovate, sub-compressed; centre of each valve longitudinally depressed; with 
77 * ^ T u ^ en * s * (Voting Atrypa.) Longitudinally ovate, convex, smooth, curved; base pointed; valves equal. 
t , ndata. {fl r at>eci Atrypa.) Transversely elliptical, inflated, smooth; one valve, with central elevation leading to linguiform simiq 
Length, 3 in. ; breadth, 1J in. 6 IU1 Binus * 
.7**’ ?9» 79*. A. Depressa. (Depressed Atrypa.) Transversely obovate, compressed, smooth; sides depressed ; base elevated; beaks impmoi • 
with three or four, longitudinal sulci in centre. Length, J in.; breadth, 4 in. unequal, 
, .60* A. Tenulstriata. (Thin-Striated Atrypa.) Transversely ovate, gibbose; beaks small, waved, bent; base, with narrow protrusion* wlfh 
longitudinal stnte. Diameter, 1} in. 1 
al’Pl&nostllcata. (Flat-furrowed Atrypa.) Pentahedral; sides rounded, depressed ; with undulating fringes. 
83, 84. A. Implexa. (Flatted Atrypa.) Transversely obovate; base straight, flat; with many, acute plaits, forming toothed margin* with 
edges of valves locked into each other. b » uu 
( 63 ) 
