LICHAS (PLATYLICHAS) GRAYI. 101 



our knowledge of the critical characters of the head-shield. One from Mulloch 

 Hill (now in the Museum of Practical Geology) was figured by Nicholson and 

 Etheridge (op. n't.) as L. barrandei?, but it differs from that species in several 

 important particulars, as the following description shows : 



Pygidium parabolic, wider than long. Axis subcylindrical, convex, less than 

 one third the width of the pygidium, and about half its length ; extremity rounded, 

 undefined. Articulating half-ring present on front end of axis followed by three 

 complete well-marked rings and a fourth faintly defined one. Axial furrows straight 

 at sides of axis, curving inwards gently at its extremity, produced behind it, and 

 near their blind ends again curving outwards, but not reaching posterior margin. 

 Post-axial piece flattened, about half the length of pygidium, enclosed for its anterior 

 two thirds by the produced axial furrows. Lateral lobes flattened, consisting of three 

 pairs of pleurae, each with a pleural furrow, and ending in short free points on the 

 margin. First pleura increasing in width to remote fulcrum, beyond which it tapers 

 rapidly to short recurved free point. First pleural furrow parallel to first interpleural 

 furrow, which makes an angle of about 45° with the front edge. Second pleura 

 marked by pleural furrow with second interpleural furrow nearly parallel to it, and 

 making an angle of about 60° to front edge of pygidium. Third pleura with short 

 median furrow, and only partially marked off from post-axial piece by the incomplete 

 produced axial furrows. The third pair of pleurae end in short free points closely 

 placed together, giving a characteristic bifurcate appearance to the pygidium. 

 All the furrows on the lateral lobes are apparently of equal strength, and the whole 

 surface of the pygidium is tuberculate. 



Two hypostomes, one from Rough Neuk, Mulloch, and the other from "Wood- 

 land Point, in Mrs. Gray's collection, which may belong to L. grayi var. scoticus, 

 have the following characters : 



Transversely subquadrate in shape, with gently convex body, nearly twice as 

 wide as long, and enclosed by strong furrows. Front of body strongly arched 

 forward, sides straight, converging posteriorly at about 60° — 70°, posterior end 

 gently arched backward ; sides of body indented at about two-thirds their length 

 by deep, short, slightly oblique furrows, expanding at their inner ends and 

 leaving a narrow transverse lobe behind them. Border wide, flattened, expanded 

 and swollen at sides, and forming a pair of broad, rounded, posterior marginal 

 lobes, more than half as long as the body. Posterior notch between them wide 

 and shallow. Surface of body ornamented with coarse granulations ; surface of 

 border marked with faint striae parallel to its outer edge. 



Collections. — Mrs. Gray (f. M.) ; Museum of Practical Geology (f. M.) ; Wood- 

 wardian [Sedgwick] Museum. 



Horizons and Localities. — Mulloch Hill Group (L. Llandovery) : Mulloch Hill ; 

 Craigens ; ? Rough Neuk. ? Saugh Hill Group (M. Llandovery) : Woodland Point, 

 Camregan Group (IT. Llandovery) : Camregan Wood. 



