Mr. T. R. Jones on Beyrichise. 1 67 



Ludlow) ; Llaufair Road, W. of Welchpool (Wenlock shale) ; 

 [Gaer Fawr, Montgomeryshire (Upper Bala) ?] ; and the sand- 

 stone of Boocaun and the slates of Cappacorcogue, Cong, County 

 Gal way. 



B. Klcedeni, var. antiquata. PL VI. fig. 8. 



Fig. 8 represents a veiyiine dextral valve, clearly referable to 

 this species, but differing from the typical form in its greater 

 proportional length and squareness, — the relative shortness of 

 the anterior lobe, — the greater development of the marginal 

 rim, which has its outer edge furnished with strong spines, — 

 and especially in the finely punctated surface of the valve. I 

 found this specimen in a calcareous nodule, containing Grapto- 

 lites and Orthoceras subgregarium, from the Wenlock schists in 

 the road-cutting about half a mile from Montgomery towards 

 Garth Mill. 



B. Kloedeni, var. torusa. PI. VI. figs. 10, 11, 12. 



Accompanying specimens of the tj^pical form (fig. 9) in soft 

 light bi'own micaceous shale of the Upper Ludlow series, from 

 Frith quai-ry, Stapleton, near Presteign, are numerous indi- 

 viduals of B. Klcedeni in which the anterior and posterior lobes 

 are each divided into two knobs, which with the central boss 

 make the valve 5-lobed (figs. 10, 11). The infero-anterior lobe 

 attains in the larger specimens a great (relative) size, and over- 

 hangs the ventral border. The valve is more quadrate, and the 

 marginal rim is better developed, than in the usual smaller 

 3-lobed form. 



The specimens occur as impressions on a divisional plane of 

 the rock. (Mus. Pract. Geol.) 



In greenish clayslate from the lowest beds at Wooltack, Pem- 

 broke (Mus. Pract. Geol.) occurs an imperfect impression of a 

 very large individual of this variety. The anterior lobe is oblique 

 and subdivided into three tubercles, the lower one large and 

 overhanging the ventral border, the other two deci-easing rapidly 

 in size upwards. The central lobe is represented by two trian- 

 gular knobs, and the posterior lobe appears to be pyriform and 

 curved, but is not well preserved. 



This variety may be the result of age, especially as the greater 

 development of the isolated lobes appears to accompany increase 

 of the size of the valve. Still there appears to be a want of an 

 intermediate stage between the forms represented by figs. 9 

 and 10. 



At first sight, fig. 12 appears to bear a close resemblance to 

 Kloden's fig. 22 (pi. 1 . Verstein. Mark Brandenburg, &c.) ; but 



