Vol. 54.] 



FAUNA 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 the 

 general 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 aperture 

 and immediately grows out. It 

 varies in length from | to 1^ inch 

 (12*7 to 38 mm.) ; the maximum 

 width, -^Q^inch ('87 mm.), is attained 

 almost at once ; there is no percep- 

 tible increase after the two earliest 

 thecae. 



The stipe has in general a more 

 rigid look than in Az. Lapworthi, 

 though it is often curved in its more 

 distal part. 



Occurrence. — On the same slab 

 with Didymograptas patulus (Hall), 

 D. gibherulus, JN'ich., and also in 

 dense masses to the exclusion of 

 other species (at Barf). Top of 

 Middle tSkiddaw Slates. This species 

 had not hitherto been recorded from 

 this country. 



Localities. — Barf; north-east 

 of Sleet How, west of Braithwaite ; 

 Carlside Edge. 



cicus from Barf; coll, 

 Woodwardian Museum. 



[X 10.] 



[X2.1: 





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 Azygograptus 

 appeared in the following order : — (1) Az. Lapivorthi ; (2) Az. 

 suecicus ; (3) Az. coelebs. 



Az. Lapworthi is found in Hodgson How Quarry, near Portinscale, 

 associated with Dicliograptus octobrachiatus (Hall) : immediately 

 outside the village of Portinscale there is in the road-cutting an ex- 

 posure of Skiddaw Slates, which, from their position, should represent 



