Mr. T. R. Jones on Beyrichise. 165 



The black Bala flagstoue of Abermavchant (in the Museum of 

 Practical Geology) contains specimens of B. complicata in which 

 the furrows are not so deeply excavated as in the Llan j\Iill 

 specimens. Hence the ridges are broader and less steep, the 

 connecting ridge along the ventral border more distinct, and the 

 aspect of the valves approaches that of some of our Corrugatce ; 

 thus making the passage still less difficult between our B. Ribei- 

 riana, Barrande's B. Bohemica, and the typical B. complicata. 

 There is here and there on the Abermarchant specimens some 

 slight evidence of a granulated surface. 



B. complicata, var. decorata. PI. ^'^I. fig. 6. 



Accompanying the broad-ridged form of B. complicata in the 

 Abermarchant flagstone (Mus. Pract. Geology), is an impression 

 of the valve of a variety of this species, which has a semicircular 

 outline, a finely granulated surface, and a broad, depressed, 

 sloping marginal rim, which was crested by a continuous series 

 of fine projecting spines. The ridges are disposed in much the 

 same manner as those in fig. 5 and in McCoy's spjcimen above 

 referred to, the bifurcation of the posterior ridge being vertical ; 

 the furrows are very strongly marked ; the middle ridge is some- 

 what crenulate, and the anterior lobe is impressed by a slight 

 indentation along its thickest part. 



Beyrichia complicata is a characteristic Lower Silurian form ; 

 its localities above alluded to are — Llan ]\lill, near Narberth ; 

 Harnage, near Shrewsbury ; and Abermarchant. Prof. M'Coy 

 mentions as localities for this species — 



LlanfwTog, near Ruthin. 



Cwm of the Cymmerig, E. of Bala. 



Hill N. of Moel Uclilas, Montgomer}'shire. 



Tregib, S. of Llandeilo. 



Coed-y-Bedw Bala I Upper Bala. 



belattyn Koad, S. oi LlaugoUen. ' 



Bryn Eithin, Penmachno. 



Mynydd Mawr, Caermarthenshire. 



Mathyrafal, S. of Meifod. 



Pen-y-Park, Llanfyllin. 



Pont-y-Meibion, two miles S. of Llansantfraid, on "] 



the Ceiriog. I Lower Bala. 



Milltir Cerrig, Llangynnog, Montgomeryshire. J 



2. Beyrichia Klcedeni, M'Coy. PI. VL figs. 7 & 9. 



Synops. Sil. Foss. Ireland, 1846, p. 58 (woodcut figs.) ; Brit. 

 Pal. Foss. Cambridge, 1851, part 2. fasc. J. p. 135. pi. 1 E. 

 fig. 2. Ac/nostus tuberculatus, Sil. Syst. 1839, p. 601. pi. 3. 

 fig. 17 (non Battus tuberculatus, Kloden). Beyrichia tuber culata, 



