8 Bolton, Palcsontohgy of the Manx Slates. 



Prolonged search resulted in the discovery of two 

 small splintery masses of slate, each bearing Dictyonenta 

 and Dendrograptus in association. The former genus was 

 most numerous, fragments of nearly a dozen individuals 

 \ being present ; of the latter genus only two specimens 

 were clearly distinguishable. 



Dictyonenia (Dictyograptus) sociale Salter. {Plate i, 

 figs. I, 2.) 



Remains of not less than eight individuals were found 

 lying in close apposition upon the surfaces of two narrow 

 splintery slabs of slate. 



Two individuals are fairly well defined, and show 

 clearly the bifurcation of the branches. Each consists of 

 about six main branches which bifurcate twice, and are 

 arranged parallel to one another in the close radiate order 

 so characteristic of the species. 



Transverse filaments, or dissepiments, are not well 

 defined, except in the case of the tertiary branchings where 

 they are very oblique. 



On one slab, the individuals lie without any order as if 

 drifted there ; on the other, three individuals lie at equal 

 distances apart and pointing in the same direction, and are 

 at right angles to a specimen of Dendrograptus flexuosus. 



A direct comparison of the Isle of Man specimens with 

 well-defined forms of D. sociale obtained from Borth, 

 Tremadoc, Wales, shows a close similarity, extending 

 even to the character of the rock, and the abundant 

 presence of iron-staining in both. 



Dendrograptus flexuosus Hall. {Plate i, figs, i, 2.) 



Fragments of three individuals of this species are 

 associated with those of Dictyonenia sociale already 

 described. The frond expands rapidly and consists of 

 short flexuous branches which bifurcate regularly and at 



