The Quarterly journal of the Geological Society of London . UNA OF THE SKIDDAW SLATES. 515 are inclined at an angle of 15°. The apertures of the thecse are straight, Fig. 29.—Azygograptus sue- acute, and perpendicular to thegeneral direction of the stipe. The sicula is very long and narrow,it is fully j\ inch (1*58 mm.) long ;the stipe arises close to the apertureand immediately grows out. Itvaries in length from | to 1^ inch(12*7 to 38 mm.); the maximumwidth, -^Q^inch (87 mm.), is attainedalmost at once ; there is no percep-tible increase after the two earliestthecae. The stipe has in general
The Quarterly journal of the Geological Society of London . UNA OF THE SKIDDAW SLATES. 515 are inclined at an angle of 15°. The apertures of the thecse are straight, Fig. 29.—Azygograptus sue- acute, and perpendicular to thegeneral direction of the stipe. The sicula is very long and narrow,it is fully j\ inch (1*58 mm.) long ;the stipe arises close to the apertureand immediately grows out. Itvaries in length from | to 1^ inch(12*7 to 38 mm.); the maximumwidth, -^Q^inch (87 mm.), is attainedalmost at once ; there is no percep-tible increase after the two earliestthecae. The stipe has in general a morerigid look than in Az. Lapworthi,though it is often curved in its moredistal part. Occurrence.—On the same slabwith Didymograptas patulus (Hall),D. gibherulus, JNich., and also indense masses to the exclusion ofother species (at Barf). Top ofMiddle tSkiddaw Slates. This specieshad not hitherto been recorded fromthis country. Localities.—Barf; north-eastof Sleet How, west of Braithwaite;Carlside Edge. cicus from Barf; coll,Woodwardian [X 10.] [: Az. Lajpworthi Az. codehs Az. stiecicus Length of sicula ^0 in. (1 26 mm.) ^V in. (-87 mm.) Jg in. (1-58 mm.) Origin of stipe on sicula half way down base angle side & base Character of stipe ... flexuous horizontal rigid at first Number of thecae (1) to (1) twenty (1) twenty-five (1) eighteen inch, (2) in 10 mm. (2) eight (2) ten (2) seven Cell-inclination 20° 15° 15° Max. width of stipe ... ^V in. (1-05 mm.) 3:V in. (-5 mm.). ^V in. (-87 mm.) Divergence of stipe ..- 110° perpendicular 145° Note on the Azygograpti. There can be, I think, little doubt that the species oi Azygograptusappeared in the following order :—(1) Az. Lapivorthi; (2) ; (3) Az. coelebs. Az. Lapworthi is found in Hodgson How Quarry, near Portinscale,associated with Dicliograptus octobrachiatus (Hall): immediatelyoutside the village of Portinscale there is in the road-cutting an ex-posure of Skiddaw Slates, which, from the
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Keywords: ., bookcentury1800, bookdecade1840, bookidquarte, booksubjectgeology
