1909. CarruThers & Muff. — Palcsozoic Rocks of Killaiy. 11 



of schist and augular lumps of vein-quartz, overlain by a 

 small thickness of red mudstones and barren green grits. The 

 latter are succeeded by calcareous shell\- grits, which have been 

 tracedfrom the Maam valley westward to a point south of Lough 

 Muck. The fauna is essentially a brachiopod one, RhyncJio- 

 nclla llandoveriana being the most abundant species. Although 

 no characteristic Llandovery fossil has been found in the 

 shell-beds of this district, it should be noted that the Survey 

 fossil lists record Peiifai/ienis oblongjcs from this horizon at 

 several points to the eastward, and we have obtained this fossil 

 from another outcrop of these shelh^ grits near Cregganbaun, 

 some miles N.N.W. of Doolough. 



The shell-beds are succeeded bv a massive conq-lomerate 

 composed of large well-rolled boulders of quartzite mixed with 

 a few of igneous rocks, generally porphyrite, but the granite 

 boulders which are so abundant in the Aienig grits are absent 

 here. The overlying beds, completing the Owendnff Series, 

 are a thick series of coarse, grey wacke grits, alternating with 

 green, sandy slates. On the north side of Lough Fee a thin 

 dark band in the slates yields numerous specimens of HIoiiO' 

 graptus riccartonensis, and a higher band about 300 feet below 

 the top of the group contains Monogi'aptus vomerinus. It is 

 evident therefore that the upper part of the Owenduff Series 

 represents the Wenlock stage. 



The overlying group, the Salrock Slates, is the highest in 

 the district. It presents throughout a monotonous succession 

 of dull Indian- red and pale green slates upwards 013.000 feet 

 in thickness. Fossils are extremely scarce, but those found 

 are characteristic of the Ludlow group — Lingula Davisi, L. 

 Syniondsi, and Modiolopsis complanata. 



The succession of the various rock groups is summarised in 

 descending order, in the following table : — 



r Salrock Slates. (Ludlow). 

 Silurian. { Owenduff vSeries. (Wenlock and Upper 



^ Llandovery). 



r Mweelrea Grits {sc7is2i originalc). (Bala (?) 

 and Llandeilo). 

 Doolough Slates, Leenane and Rossroe 



Grits. (Upper Arenig). 

 Black slates and cherts at Bencraff. (Middle 

 Arenig). 

 33 George Square, Ediubiugb. 



Ordovician. 



