Mr. T. R. Jones on Beyrichise. lil^^ 



The black Bala flagstone of Abermarehant (in the Museum of 

 Practical Geology) contains specimens of B. complicata in which 

 the furrows are not so deeply excavated as in the Llan Mill 

 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 Corrugata ; 

 thus making the passage still less difficult between our B. RibeU 

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

 There is here and there on the Abermarehant specimens some 

 slight evidence of a granulated surface. 



B, complicata, var. decorata. PI. VI. fig. 6. 



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

 Abermarehant 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 specimen 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. IJt // 



c Beyrichia complicata is a characteristic Lower Silurian form ; 

 its localities above alluded to are — Llan Mill, near Narberth ; 

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

 mentions as localities for this species — 



. Llanfwrog, near Ruthin. 

 *- i'fCwm of the Cymmerig, E. of Bala. 

 ano.tflill N. of Moel Uchlas, Montgomeryshire. 

 j^ff j Tregib, S. of Llandeilo. 

 i Ooed-y-Bedw, Bala. 



Selattyn Road, S. of Llangollen. 



Bryn Eithin, Penmaehno. 



Mynvdd Mawr, Caermarthenshire. 



Mathyrafal, S. of Meifod. 

 . y^jjPen-y-Parkj, Llanfyllin. 



Jo J-^rPont-y-Meibion, two miles S. of Llansantfraid, on"| 

 \^\'] the Ceiriog. K Lower Bala. 



Milltir Cerrig, Llangynnog, Montgomeryshire. J 



2. Beyrichia Klcedeni, M^Coy. PI. VI. figs. 7 & 9. 



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

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

 fig. 2. Agnostus tuberculatus, Sil. Syst. 1839, p. 604. pi. 3. 

 fig. 17 (non Battus tuberculatus, Kloden). Beyrichia tuberculata, 



► Upper Balii. ' 



