Vol. 54.] 



FAUNA OF THE SKTDDAW SLATES. 



471 



Eig. 3. — Bryograptus ra- 

 mosus var. cumbrensis. 



This specimen appears to differ from the typical Br. Callavei in 

 (1) wider divergence of stipes ; (2) greater number of thecae to the 

 inch, twenty-eight instead of twenty. 



The specimen was figured by Marr (Geol. Mag. 1894, p. 130, 

 fig. 6). 



Occurrence. — Lower Skiddaw Slates. 



Locality. — Barf, near Keswick. 



(a) Beyogkaptus eamostjs, Brogger, var. cfmbrensis nov. 



The rhabdosoma consists of two slender primary stipes diverging 

 from a large (J^g- inch, 1*58 mm.) and 

 clearly defined sicula at a small angle. 

 The virgula is sometimes well preserved. 

 From the inner margins of the primary 

 stipes originate two or more compound 

 secondar}^ branches. These are unsym- 

 metrically disposed, and may arise near 

 the sicula or quite remote from it. The 

 thecse number twenty-four to the inch 

 (nine to ten in 10 mm.) ; they are widest 

 at their apertures ; their outer walls are 

 straight or very slightly curved. They 

 are in contact with each other for rather 

 less than half their length, and are in- 

 clined at an angle of about 20°. The 

 apertures are concave, and the apertural 

 angle varies between 115° and 120°. 



The irregular and un symmetrical 

 branching shows the near relationship 

 of this form to Brogger's typical Br, 

 ramosus. But in the variety here de- 

 scribed the secondary branches may be 

 near the sicula or remote from it, whereas 

 Brogger states that in the typical form 

 they are always remote. This variety, 

 then, differs from the typical form 



(1) In the position of the irregularly 

 disposed secondary branches. 



(2) In the number of thecae to the 

 inch; Brogger's type having forty 

 to fifty in the inch (sixteen to 

 twenty in 10 mm.), whereas in 

 this variety the number never ex- 

 ceeds twenty- four (nine to ten in 

 10 mm.). 



Br. ramosus var. cumbrensis differs 



from Br. KjeruJJl^ Lapw., to which it 



has sometimes a superficial resemblance, 



(].) In unsymmetrical branching. 



(2) In the character of the cells, and 



their number to the inch. 



Nat. size. 



[Colls. Postlethwaite & 



Woodwardian Mus.] 



Fig. 4. — Diagram shoiu- 

 ing the point of origin 

 of the earliest theca 

 {see also Jig. i, j?. 4-^0). 



Hen- J 



[xlC] 



