476 J. E. MARK AND T. EOBEETS ON THE 



35. The Lower Pal-^ozoic Eocks of the ISTEiGBiBOirEHOoD of Hayer- 

 FORDWEST. By J. E. Marr, Esq., M.A., F.G.S., Eellow of* 

 St. John's College, Cambridge, and T. Eoberts, Esq., B.A., 

 E.G.S., St. John's CoUege, Cambridge. (Bead June 10, 1885.) 



[Plate XV.] 



§ 1. Introductory, 



The country around Haverfordwest is of great interest to geologists, 

 first, on account of the evidence furnished therein of the relations 

 of the graptolite-bearing beds to the strata which are characterized 

 by the presence of higher organisms, and secondly, from the nature 

 of the foldings which the rocks of the district have undergone. 



"We propose, in this communication, to devote our attention to the 

 former of these subjects. 



Our work is based upon that which has been done by the Greo- 

 logical Survey, and published in Sheet 40, Horizontal Sections, Nos. 

 1 & 2, and Mem. Geol. Survey, vol. ii. part i. 



Whilst fully acknowledging the great value of these publications, 

 we think it desirable, now that our knowledge of the forms of life 

 occurring in these rocks has been so much increased by the labours 

 of many geologists in recent years, to attempt a more minute classifi- 

 cation of the rocks of this district than that adopted by the Govern- 

 ment Surveyors. In our opinion, this further description of the beds 

 will throw considerable light upon the character of the movements 

 which the district has undergone. 



Our thanks are due to Dr. Hicks for the very kind way in which 

 he placed a series of specimens collected by himself at our disposal. 

 We have also to thank Prof. Lapworth for his kindness in examining 

 our collection of graptolites. 



The area which we have chiefly examined is a well- defined tract 

 (see Map, PL XV. fig. 1), about eighteen miles in length from east 

 to west, and having an average breadth of five miles, lying to the 

 north of the towns of Haverfordwest and JS'arberth. It is bounded 

 on the north by a great fault, running from Eoch Castle in an 

 easterly direction, along the margin of a mass of rock which Dr. Hicks 

 has claimed as Pre-Cambrian. On the west and south, the Lower 

 Palaeozoic rocks of this tract are succeeded by Old Eed Sandstone 

 and Carboniferous deposits, and on the east, a considerable extent of 

 Llandeilo limestone is represented on the Geological Survey map. 



Within this area is a portion of a wide sjiiclinal, complicated by 

 minor foldings, running from near CljTiderwen Station on the east, 

 to the Coal-measures on the west. South of this is a complicated 

 anticlinal in the neighbourhood of IS'arberth. 



§ 2. Establishment of the Succession. 

 1. Lingula Flags. — To the north of the great fault alluded to as 



