Mr. T. R. Jones on Beyrichiae. 171 



until it is elevated into a strong conical projection or spine. The 

 marginal rim is well defined, and was furnished with a series of 

 thin projecting spines. 



This well-marked and peculiar species is established on a 

 distinct impression (somewhat squeezed obliquely by the cleavage- 

 structure of the rock), discovered by Mr. Salter in the Lower 

 Llandeilo schist of Mynydd Garw, Beddgelert, N. Wales. (In 

 the Museum of Practical Geology.) 



I have dedicated this Beyrichia — the earliest, so far as yet 

 known, of the genus, and one of the most peculiar" — to M. Bar- 

 rande, of Prague, whose indefatigable and extensive researches 

 in the palaeozoic rocks of Bohemia will have comprised the study 

 of the Beyrichice and their allies, as well as the larger and more 

 important groups of organic life, some of which M. Barrande has 

 already so elaborately and lucidly illustrated. 



(SlMPLICES.) 



8. Beyrichia stranguluta, Salter. PI. VI. fig. 18. 



Brit. Pal. Foss. Cambridge, part 2. fasc. 1. p. 136 (M'Coy's 

 descript.), pi. 1 E. figs. \a, lb; and fasc. 2. Appendix A. p. ii. 

 {Salterns descript.). 



Carapace-valves subquadrate, convex; impressed at or near 

 the dorsal border, and towards the narrow (anterior) end of the 

 valve, by a short, vertical, subcentral furrow ; the anterior side 

 of the furrow rising up in a low rounded knob or tubercle. 



The marginal rim is very broad, convex, divided from the 

 body of the valve by a deep narrow furrow, and is seldom well 

 preserved. From Mr. Salter's obseiwations [luc. cit.), the mar- 

 ginal rim would appear to be broader at the antero-inferior, tli:m 

 at the posterior border of the valve. Prof. M'^Coy says that the 

 marginal rim is often wanting, having been broken away. 



B. strangulata is abundant in the Upper Bala calcareous 

 schists at Coniston Waterhead, Lancashire. 



The foregoing description of the typical specimens is not 

 quite applicable to any of the forms that I have next to notice. 

 Still I see no good reason for regarding as distinct species the 

 individuals represented by figs. 19-22; for, although neither of 

 them exactly corresponds with the above description, yet there 

 are some important characters common to all, especially the 

 uniform convexity of the valve, and the single dorsal sulcus. On 

 the other hand, there is a considerable, though not an unlimited, 



12* 



