486 Walter Keeping — Fossils from Central Wales. 



sombre grey in the maps of H.M. Geological Survey. And even 

 now, after my laborious search in that country, it cannot be said to 

 be anything better than very poor in organic remains. 



We have, however, now found a considerable number of speci- 

 mens, and, what is more important, the species are quite sufficient 

 to establish the exact age of the Cardiganshire group of rocks, and 

 determine their order and succession. They belong to the Lower 

 Llandovery period. 



, The most important of the fossils found belong to the group of 

 GraptoUtes, of which I have already given an account with the kind 

 help of Prof. Lapworth.^ But there are other fossils and markings 

 of great interest which have been reserved until now for description, 

 although their names are already published. They form the subject 

 of the pi'esent paper. 



There has been some discussion of late^ on the nature of such 

 obscure markings as o'ccur in the Aberystwyth grits, and perhaps 

 the impression of many naturalists that they are of inorganic origin 

 has been increased. Doubtless there are in the Cardiganshire rocks 

 many markings of that nature, but the things I here describe are 

 not such, but are structures of such distinct type and regularity of 

 form as to leave no room for doubt of their organic nature. 



The very ancient Foraminifera here described, and the fact of 

 their close resemblances to modern forms, are also matters of 

 particular interest. 



The Aberystwyth rocks abound in exti-aordinarj'' markings of con- 

 cretionary or other origin, and great beds of rock have been re-made 

 by these agents, but I find in most cases little difficulty in deter- 

 mining which of the peculiar structures are of organic origin and 

 which are not. 



Many even of the irregular conci'etions have had their first origin 

 in some organic structure such as the position of a seaweed, or even 

 the track of a worm ; but these imperfectly marked structures I have 

 not recorded in this paper, only describing the thoroughly well- 

 marked types of whose organic nature there is no room for doubt. 



Desckiption of Fossils fkom the Cardiganshire Group. 



Plants. — The remains of plants are very conspicuous in the rocks 

 of Cardiganshire, especially in the Aberystwyth Grits. In many cases 

 we meet with the well-known difficulty of distinguishing between 

 true plant structures and worm markings, but some of the vegetable 

 remains are perfectly clear and indisputable, such as, for example, 

 the various forms of fan-shaped Algee of the Genus Biiihgtrephis. 



Another type of vegetable structure is seen in the Net Algal 

 (Retiofucus extensus, n. sp.), which consists of substantial bar-like 

 structures, similar to bodies which are very generally referred to 

 worm casts. The vegetable nature of this structure cannot however 

 be doubted, as an inspection of the figure will show (see PI. XI. Fig. 

 6), and it cannot possibly belong to the Annelida. We are thus 



1 Quart. Journ. Geol. Soc, May, 1881. 



2 jSTathorst, Geol. Mag. 1882, p. 24. 



