Walter Keeping — Fossils from Central Wales. 489 



the Chondrites figured by M'Coy from the Skiddaw Slate ; and some 

 are worm markings. 



Fragments similar to the Palieophyciis (?) striatus of Prof. Hall, 

 are not imcommon, and certain long square rods remind one of Pal. 

 simplex, Hall. But I doubt whether these are organisms at all. 



Nematolites. — These are curious irregular branching structures of 

 widespread occurrence in Cardiganshire. They are always found as 

 solid bodies of pale chocolate colour and earthy constituency, spread- 

 ing out in a loose manner over the dark shales, from which they may 

 often be easily isolated and mounted free of rock. Good specimens 

 may be collected on Craiglais. With the magnifying glass and 

 microscope no cells or other structures can be detected upon the sur- 

 face, but some specimens show decided indications of a central axis. 

 By preparing thin sections for the microscope this axis is shown 

 to be only the dark argillaceous rock matrix, so that the original 

 stem was fistular (see PL XL Fig. 10) ; the thickness of the walls 

 being less than the diameter of the interior of the tube. No minute 

 structure is preserved in the walls. 



I i-egard these bodies as forms of Coralline Algas, the stems 

 having been originally rigid and calcareous. It is probable that the 

 Nematolites Grayii (Lapw.) of the Girvan district is of the same 

 nature. 



There appear to be two species in Cardiganshire. 



1. Nematolites Edioardsii, n. sp. PI. XI. Figs. 8-11. 



Plant calcareous, branching, consisting of long wire-like cylindrical 

 stems of uniform thickness (1 mm.), sometimes straight, but usually 

 with irregular curves and twistings. Branches are given off in a 

 most random manner, a stem often remaining perfectly simple for 

 several inches and then giving off quite a bush of branches, or even 

 forming a network. Still, the general build is very open and loose. 

 The branches are of the same claaracter as the main stems, and there 

 is no perceptible diminution in their thickness. The included angle 

 of division varies from an acute angle to a right angle ; commonly 

 it is very wide, i.e. nearly a right angle. Occasionally these 

 branches coalesce or are bound together by a cross branch so as 

 locally to form a network. 



Localities. — In the Aberystwyth Grits and Metalliferous Slates at 

 Craiglais, Aberystwyth ; Ty Llwydd on the Eheidol ; Devil's Bridge 

 above Taliessin, Llantrisant, Dyffryn Castell, East of Devil's Bridge. 



Similar bodies occur in the Arenig rocks of Barf near Keswick 

 and Ellengill. See specimens in the Musevun of Practical Geologj^ 

 iv. 4. 42-44, called '• branching Polyzoon." See also Salter in Quart. 

 Join-n. Geol. Soc, vol. xix. p. 137, fig. 14. 



Also last year (1881) I found this structure in the grits of Hodgson 

 How, Keswick, in a rock which is identical with the Aberystwyth 

 group. 



2. Nematolites dendroidium, n. sp. PI. XI. Fig. 12. 

 Distinguished from the other species by having a distinct trunk 

 and main stems, from which smaller lateral branches are given off. 



