170 Mr. T. R. Jones on Beyrichise. 



Ribeiro, who brought these Portuguese fossils to light) occurs 

 plentifully, as casts, with B, Bussacensis in the Porto de Louza 

 schist. When examining these schists in 1853, I overlooked 

 this species, regarding the casts as crumpled specimens of a 

 large variety of B. simplex. The corrugations of the surface, 

 however, are quite constant and peculiar, as well as the outline of 

 the valves, which differs from that of B. shnplex. I have already 

 mentioned {supra, p. 91 & p. 165) that B. Bohemica (in which 

 the lobes are much more pinched up and ridge-like) forms a 

 passage from this species to B. complicata. 



6. Beyrichia affinis, nov. sp. PI. V^I. fig. 16. 



Carapace-valve depressed ; nearly semicircular, but obliquely 

 acute at one extremity (anterior). Surface of valve, if regarded 

 as 2-lobed, may be described as being divided into two parts by 

 a deep and broad central indentation ; the anterior part of the 

 valve forming a somewhat convex, pyriform, curved lobe, taper- 

 ing downwards and backwards ; the other portion of the surface 

 subdivided by a short furrow on its dorsal part and forming a 

 depressed, bifurcated, Y-shaped lobe, the anterior arm of which 

 is more prominent than the other, and constitutes a middle lobe, 

 if the valve be regarded as 3-lobed, — in which case, besides the 

 pyriform, curved, anterior lobe, there are two less prominent 

 lobes, which are near together, occupying the broad (posterior) 

 half of the valve, and are separated from the anterior lobe by a 

 broad central pit ; the middle lobe small, but well defined ; pos- 

 terior lobe larger, but depressed, curved. Marginal rim distinct, 

 especially on the posterior border. 



This little Beyrichia is essentially different from any other 

 that I have seen, although it is not without points of resem- 

 blance to some of the above-mentioned forms, such as B. Kloedeni 

 and B. Ribeiriana ; and hence I propose to distinguish it by the 

 name of B. affinis. 



It is represented by the cast of a single valve in a Lower 

 Silurian dark-coloured schist from Waterford, Tramore. (In the 

 Museum of Practical Geology.) 



7. Beyrichia Barrandiana, nov. sp. PI. VI. fig. 17. 



Carapace-valve nearly semicircular ; surface divided by a sub- 

 central furrow into two unequal lobes ; the smaller lobe is pyri- 

 form, tapering downwards ; the other triangular and subdivided 

 by a faint vertical furrow, and its largest portion, occu])ying the 

 middle of the valve, gradually rises towards the ventral border 



