LOWER PALEOZOIC EOCKS OF HAVERFORDWEST. 479 



Ogygia BucTiii. In that zone we find Turrilepas sp., Pleurotomaria 

 and OrtJioceras. SipJionotreta micula also occurs in abundance, as 

 well as in lower zones, and other horny brachiopods are common. 



5. Roheston WatJien Limestone. — This deposit is best known as 

 occurring at the village of Robeston Wathen, where a quarry to the 

 north of the church contains a black limestone with interbedded 

 black shales, dipping S.S.W. The calcareous bands are crowded 

 with Hall/sites catenulariiis, and other fossils occur, including Orthis 

 elegantula., Dalm. Trilobites are rare and fragmentary. 



(It is to be noticed that many of the fossils from this locality in 

 the Jermyn-Street Museum are not from this limestone, but from 

 higher beds, to be described presently.) 



As the section here is an important one, a figure of it is added 

 (PI. XV. fig. 3). 



The graptolite-shales are seen by a stream immediately below the 

 quarry, dipping under the limestone. These shales belong, as stated 

 above, to the Ortliis-argentea zone, and the limestone itself appears 

 to be a calcareous development of the upper part of these shales. 



Gonfirmatory Sections. — jSTear Grondre, two miles north-west of 

 Eobeston Wathen, the same limestone is seen, as represented on the 

 Geological Survey map. It is crowded with Malysites, as at Robeston 

 Wathen, and is here nearly vertical. In a quarry, at this place, the 

 black limestone is associated with an ashy-looking limestone which 

 yielded a cystidean, and which is apparently the representative of 

 the lowest stage of the next series ; but the relations of the two were 

 not determined. Possils of the black limestone at Grondre : — 



SyringophjUum organum, Li7in. 

 Halysites catenularius, Linn. 

 Petraia asquisulcata, M' Coy. 



To the north-east of the limestone quarry, in a small quarry in a 

 field close to Grondre farm, the Orthis-argentea shales are dipping 

 north. The limestone strikes as though it would pass above the 

 shales. The tract between Grondre and Eobeston Wathen is much 

 disturbed, newer beds being faulted and folded in. 



At Llandewi Yelfry, the Orthis-argentea shales, which occur 

 some way above the Llandeilo limestone, pass up into flaggy black 

 limestone like that of Eobeston Wathen. 



At Fron, 1| mile north-east of Llandewi Yelfry, where the Llan- 

 deilo limestone is not seen, the Ortliis-argentea shales are found in a 

 small roadside exposure, dipping a little north of west ; and on the 

 hill- side to the west of this and above it, black limestone is exposed 

 in a quarry, presenting an appearance quite similar to that of 

 Eobeston Wathen, also with abundance of Halysites, and amongst 

 other fossils the following : — 



HeUolites interstinctus, Wahl. 



dubius, Schmidt. 



Petraia sequisulcata, M'Coy. 



niaenus Bowmauni, Salt. 

 Orthis Actonige, Sow. 



elongata, Phill. 

 IHgenus Eowmaiini, Salt. 



Glauconome disticha, Goldf. 

 Orthis Actonise, Sow. 



calligramma, Balm. 



Leptsena transversahs, Wahl. 

 Strophomena rhomboidahs, Wilck. 



At Prendergast, north of Haverfordwest, the Orthis-argentea 



