96 BRITISH GRAPTOLITES. 



conspicuous sicula, and making with it an angle of 145°. Tliecse seven to 

 eight in 10 mm., long narrow tubes ; outer walls with slight double curvature, 

 seven times as long as wide, proximallj in contact only, but overlap increasing 

 distallj to one third their length ; inclination 15°. Apertural margins 

 straight, acute, perpendicular. 



Description. — The sicula is very long and narrow, 



Pia. m.-Azygooraplus suecicus, i^^-^^^ f^^^^ ^.q ^^^^ -^^ ^gj^^j.^^ . ^j^^ ^^-^^^ appears to 



arise close to the aperture, but in reality the first 

 theca arises slightly higher up, and is appressed to 

 the side of the sicula for a short distance, and 

 "^ then grows straight downward lieyond its aperture. 



The average length of each mature theca is about 

 2 mm. 



Affinities. — The size and generally rigid look of 



the whole polypary furnish characters whereby 



Proximal end, showing sicula. Figured ^^li^s spccics cau be readily distinguished from Az. 



^\:!tt,f^2^''in£^l LapwortU or Az. HicJcsvi. The stipe very rarely 



n'lxiilfijsi.*^'' '''''°''"'''' ""^ approaches the horizontal direction of growth 



characteristic of Az. coelehs, from which species it 



may further be separated by the form and number of the tliecse. 



Horizon and Localities. — Arenig, Middle Skiddaw Slates (Upper Tetra- 

 graptus beds). 



LaJce District : Barf ; north-east Sleet How, west of Braithwaite ; Carlside 

 Edge. Lleyn Peninsula : Parwyd. 



Associates, etc. — A. suecicus has, up to the present time, only been recorded in 

 Britain from the Skiddaw Slates and the Upper Arenig beds of the Lleyn Peninsula, 

 where it occurs in association with D. hirundo and D. gibberulus. It is abundant at 

 a corresponding horizon in Sweden, and seems to occur with the same associates. 

 Good specimens are known in the collections of the Keswick Natural History 

 Museum, the Woodwardian Museum, and in Postlethwaite's private collection. 



Group III. — Type Az. coelehs. 



Azygograpti in which the stipe grows in a horizontal direction ; but, 

 originating near the aj)ex of the sicula, is appressed to the latter throughout its 

 length ; the thecsc are long and narrow, and the amount of overla}) is small. 



