PLATE LIL* 
I , 2. Orthis Grandis. ( Great Orthis.) Compressed, semi-oval, short; with many, bifurcate radiations. Length, 1J in.; breadth, 2 in. 
3, 4. o. Elegantula. (Elegant Orthis.) Transversely semi-oval; larger valve, with acute, incurved beak; smaller valve with concave, 
mesial sulcus; base pointed, compressed; with fine, radiating stria). Length, £ in. 
5,6. StrigfOCephaluS BpevirostPi. (Short-beaked Strigocephalus.) Tumid, smooth, sub-orbicnlar; smaller valve orbicular; larger valve, 
extending into short, incurved umbo ; beak tumid; foramen acute, broad. 
7. 0. Virgata. (Branched Orthis.) Transversely obovate ; with about thirty, smooth radii; hinge-line arcuated. Length, g in.; breadth, 1 in. 
8,9. 0. VespePtilio. (Bat Orthis.) Semi-circular; with many, radiating ridges; upper valve convex, with longitudinal, central rib; lower 
valve convex, with deep, mesial sulcus ; sides angular. Length, $ in.; breadth, 1£ in. 
10. 0. Testudinaria. (Tortoise Orthis.) Orbicular; with many, granulated radii; upper valve convex, with incurved beak; lower valve, 
with mesial sulcus. Length, £ in.; breadth, § in. 
II. Tpigonosemus Lypa. (Lyre-forvied Trigonosemus.) Elongated ; beak of lower valve elongated; with two, longitudinal septa ; beak of 
upper valve, short, incurved; with furcated plaits, crossed by remote lines of growth. 
12,13. S. Giganteus. (Gigantic Strigocephalus.) Smooth, convex, sub-orbicular; valves equal; beak of larger valve straight, pointed, 
beneath which is rectangular-triangled, flat area ; foramen narrow. 
14. 0. Tpiangulapis. (Triangular Orthis.) Triaugular, convex; with many, fine radiations. Length, £ in.; breadth, J in. 
15,16. S. BUPtini. (Burtin's Strigocephalus.) Sub-globose, smooth; valves inflated; lower valve, with long, curved, acute beak; foramen 
long, wide, fiat at bottom. 
17,18,19. SpiPifer HetePOClitUS. f (Ileteroelite Spirifer.) Acutely pyramidal; umbo of lower valve pointed; foramen long, narrow; 
mesial fold broad, with four or five, lateral, radiating plaits, with trausverse stria). 
20,21,22. S. Biloba. (Two-lobcd Spirifer.) ObcOrdato, bilobatc, with longitudinal strife; larger valve, with incurved beak; hinge-area 
triangular. Length and breadth, £ in. 
23. S. GigantetlS. (Gigantic Spirifer.) Convex; sides cuspidate, with many , radiating ribs; front deep, emarginate ; with concentric lines 
of growth crossing ribs. Often 9 in. wide. 
24,25. S. SpeciOSUS. (Handsome Spirifer.) Transversely elongated, fusiform, convex; with broad, divergent ribs; lower valve, with deep, 
broad depression ; cardiual area broad, with parallel margins. 
26. S. StPiatUS. (Striated Spirifer.) Transversely obovate; valves convex, lower one, with wide, longitudinal canal in centre; sides, with 
many, radiating strife. Length and breadth, 1 in. 
27. 60. S. RadiatUS. (Rayed Spirifer .) Larger valve, with produced umbo and incurved beak; hinge-area sub-triangular; smaller valve, 
with double, produced rib in centre, and intermediate sulcus; with many, divergent strife. Length, 1& in.; breadth, 1J in. 
28. S. Phalsena. (Moth-like Spirifer.) Transversely elongated, sides rounded ; larger valve, with deep, mesial sulcus ; with regular, small 
ridges, beak produced. 
29. S. Obliteratus. (Obliterated Spirifer.) Convex, semi-circular; cardinal area, with acute terminations ; with elevated radiations, crossed 
by remote lines of growth; mesial sulcus shallow. 
30,31. S. Pisum. (Pea Spirifer.) Convex, lenticular, smooth, hexagonal; base truncated; beak small; cardinal area small, triangular. 
Length and breadth, £ in. 
32, 33. S. Ptychodes. (Two-folded Spirifer.) Elongated, smooth, with fine, longitudinal folds ; beak of larger valve produced, curved. 
Length and breadth, £ in. 
34. S. Afflnis. (Allied Spirifer.) Lenticular, with many, longitudinal ribs, crossed by thin lamim©; cardinal area flat, triangular; beak of 
lower valve produced. 
35, 36. S. CostatUS. (Ribbed Spirifer.) Convex, fusiform, transversely elongated; with two, central ribs and five or six, thick ones on each 
side of these ; lower valve, with broad, deep sulcus and two, strong ribs ; hinge-area broad, with parallel edges. 
37. S. InOPnatUS. (Unadorned Spirifer.) Transversely elongated, fusiform, compressed, smooth; sides, with obscure radiation; base even; 
beaks obscure. 
38. S. Extensus. (Extended Spirifer.) Convex, transversely elongated, fusiform ; with many radii; beak small. 
39. 40. Orthis Flabellum. (Little Fan Orthis.) Transversely sub-ovate ; binge-line arcuated ; one valve flat, the other convex, with slight, 
mesial channel; with about twenty-four rounded radii. Length, § in.; breadth, 1 in. 
41, 42. S. Inteplineatus. (Interlined Spirifer.) Transversely oval, convex; cardinal area wide; umbo of larger valve produced; beak, 
curved to meet beak of opposite valve ; with many, longitudinal ribs, five on each side. Length and breadth, $ in. 
43, 44. S. Tpapezoidalis. (Trapcziform Spirifer.) Semi-circular, transversely elongated ; cardinal area largo, arcuated ; foramen narrow ; 
with mesial, elevated rib from beak to base in upper valve aud with similar sulcus in lower one. 
45, 46. S. Gpandsevus. (Aged Spirifer.) Semi-elliptical; hinge-line straight, projecting ; smaller valve, with large, rounded, mesial ridge, 
with sulci on either side aud about ten radiations on both sides. 
47. S. Crispus. (Curled Spirifer.) Gibbose, transversely elongated; with five to seven plaits, crossed by strong laminae; hinge-line, with 
obtuse ends ; beak remote. Length, £ in.; breadth, J in. 
48. S. DisjunctUS. (Disjoined Spirifer.) Convex, semi-circular; base emarginate; upper valve, with about twelve, strongish ribs; lower 
valve, with many, rounded ribs, about twenty-five on each side of mesial one ; hinge-area broad, curved, with parallel edges; beaks remote. 
49. 58. S. Simplex. (Simple Spirifer.) Pyramidal; cardinal area large, triangular; mesial rib, with obtuse borders; triangular foramen; 
smaller valve convex; without ribs or sulci. 
50,51. S. PaPtitUS, (Divided Spirifer .) Round; lower valve, with deep sinus, extending to base; opposite valve, with corresponding rib; 
with three to six sulci and ribs. 
52. S. Lrovis. (Smooth Spirifer.) Transversely elongated, semi-circular, smooth, compressed; beaks of umbones prominent. Length, 3 in.; 
breadth, 1 J in. 
53. S. Caleapatus. (Spur Spirifer.) Transversely elongated, semi-circular; sides convex, cuspidate, smooth, with longitudinal sulci; with 
many ribs; cardinal area narrow. 
54. 55. S. UPii. (Ure's Spirifer.) Hemispherical, smooth ; beak inflated; base emarginate ; lower valve convex, with channelled beak ; upper 
valve compressed. 
56. S. Nudus. (Naked Spirifer.) Semi-circular ; beaks prominent, smooth; a mesial rib, with sulcus on each side; margin obtuse. 
57. S. PlicatUS. (Plaited Spirifer.) Transverselyeiongated, semi-circular, convex; with many, sharp plaits; beaks contiguous; cardinal 
area narrow. Length, 1 in.; breadth, 1J in. 
59. S. Subconicus. (Sub-conic Sjririfer.) Larger valve sub-conic, with central, longitudinal sulcus aud several strong ribs, crossed by a few 
lines of growth ; cardiual area large, triangular, flat. 
61. 0. Plicata. (Plaited Orthis.) Transversely elongated, depressed, with many, sharp plaits. 
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