Fig. 20. Horizontal section of cephalic eye 20/1. » 21. Vertical section of the same 60/1. » 22. Hypostoma 4/1. » 23-25. Samples of right maculæ 20/1. » 26. Horizontal section of macula, the portion bearing the lenses 20/1. » 27. Vertical section of the same 60/1, _a_ the lenses. Specimen from Stora Carlsö. » 28. Hypostoma 4/1. » 29. The right macula 12/1. » 30. A portion of the lenses on the macula in reflected light 30/1. The lenses are only faintly convex and encased in a white frame. The diameter of the largest lenses 0,06 millim. Specimen from Lansa, Fårö. =Bumastus barriensis= MURCH. p. 46. Fig. 31. Hypostoma 4/1. » 32. The right macula 12/1. Specim. CU from Wisby. =Bumastus sulcatus= LINDST. p. 46. Fig. 33. Horizontal Section of a cephalic eye 20/1. » 34. The same magnified 60/1. » 35. A similar, near the inferior margin and close to the surface, _a_ the eye, _b_ cheek 60/1. Compare fig. 38. » 36. Vertical section of the cephalic eye near the suture 20/1. » 37. The same, more magnified 60/1. » 38. A similar, near the inferior margin, _a_ eye, _b_ cheek 60/1. » 39. Cast of the interior surface of a hypostoma 2/1. » 40. The same seen from the side. Originals to figs. 33-38 from Samsugu, Othem, Gotland, figs. 39 & 40 from Stora Vede, Follingbo, Gotland. =Bumastus= sp. p. 47. Fig. 41. Horizontal section of cephalic eye, near the inferior margin, _a_ eye, _b_ cheek, 60/1. » 42. Vertical section of the same 60/1. » 43. A similar near the inferior margin, _a_ eye, _b_ cheek, 60/1. » 44. Hypostoma 4/1. » 45. Side view of the same. » 46. The right macula 12/1. Specimens from Korpklint near Wisby. =Bumastus= sp. p. 46. Fig. 47. Hypostoma 4/1. » 48. The right macula 12/1. Specimen from Klints, Othem, Gotland. K. Sv. Vet. Akad. Handl., Bd 34, No 8. Lindström: Trilobites. Pl. II. [Illustration] G. Liljevall del. Ljustryck af Chr. Westphal Stockholm. Pl. III. =Bumastus= n. sp. p. 47. Fig. 1. Hypostoma 4/1. Specimen AY. From Wisby, Norderstrand. » 2. Its left macula 12/1. =Bumastus= n. sp. (different from the preceding) p. 47. Fig. 3. Hypostoma 4/1. Spec. AT from Wisby, Norderstrand. » 4. Vertical section of the macula _a_ in its longest axis. » 5. A portion of the cephalic eye, the facets very low. =Calymmene intermedia= LINDSTR. p. 48. Fig. 6. Hypostoma 4/1. Spec. BG from Gotland. » 7. The left macula 12/1. =Calymmene tuberculata= BRÜNNICH p. 48 Fig. 8. The inside of the hypostoma 3/1. Spec. BA from Gotland. » 9. Horizontal section near the surface, seen from the inside 20/1.