Fearnsidks, Elles, Smith — Palwozoic Bocks of Pomeroy. 101 



only visible in walls and stone heaps along the line which we have 

 taken as our northern boundary, and, though not now exposed, would 

 seem to belong to the series under review. The general mass of the 

 Eardahessiagh beds consists of coarse to fine grained grits, with well 

 bedded calcareous flagstones at the top, and is notably micaceous 

 throughout. The lower members are always loosely consolidated, but 

 the higher ones, being well provided with Brachiopods and other fossils, 

 are rendered more compact by a calcareous cement. We were informed 

 that at one time they were much quarried for building pui^poses, and 

 also for the manufacture of flags, hearthstones, and even grindstones. 

 In general the series is thick-bedded, but, among the flaggy beds at 

 the top, quite finely laminated micaceous shales are often interstratified. 



The flagstone quarries are now closed and overgrown ; the richly 

 f ossiliferous collecting grounds which they provided to the early col- 

 lectors are therefore most unfortunately no longer available. Yv^alls, 

 however, and heaps of stone remain ; and along the high ground 

 flanking the southern slopes of Craig Eardahessiagh the process of 

 agriculture frequently brings to light richly f ossiliferous blocks which, 

 if not prolific enough to enable us to add to the long lists of Portlock's 

 collections, are more than sufficient to identify the horizon. 



The commonest fossils in the lower unconsolidated sandy beds are 

 rude casts of an Orthis like 0. calligramma. Higher up the large 

 Strophomena grandis appears in surprising abundance, and makes up a 

 very considerable proportion of the rock-forming material. It is 

 associated with Strophomena siluriana, a true Ashgillian form, and in 

 the softer beds which are interbedded with it, Illaenus, Eellerophon, 

 and various ill-preserved Gastropods are present in some abundance. 

 In the most calcareous beds, which are practically limestones, a Harpes 

 and some pieces of the liuge Lichas Mbernicus and glabellas of 

 Staurocephalus were occasionally observed. 



Under the microscope, various examples of the gritty and flaggy 

 beds show an unusual amount of fresh felspar, both oithoclase and 

 andesine ; with this is also a good deal of partly chloritized mica, a 

 serpentinous paste, and numerous detached grains of epidotic or horn- 

 blendic minerals, giving high colours between crossed nicols. A 

 crushed specimen of a less consolidated grit, when separated by means 

 of a heavy liquid (s.g. = 2-7), yielded abundant and rather large 

 tourmaline needles along with rounded red garnets, staurolite, epidote, 

 and leucoxene. "WTien weathered, the characteristic light-blue or 

 grey colour of both flags and grits gives place to a rather dull 

 gingerbread brown, which, at first affecting only the surface of the 



