LICHAPYGE ? PROBLEMATIC^. 1 ] 1 



narrow, straight, post-axial ridge to the posterior margin. Lateral lobes 

 horizontally extended, consisting of 6 — 7 pairs of pleurae, each with a well-marked 

 diagonal furrow. The first three pairs of pleurae are straight and horizontal, and 

 end in short, tapering, free spines, projecting beyond the margin and bent 

 backwards. The fourth pair of pleurae is similar, but is produced into long, 

 nearly straight spines projecting freely backwards to some little distance behind 

 the pygidium. Behind this pair the pleurae are successively curved more 

 strongly backwards till they lie almost parallel to the post-axial ridge, but they 

 have no free points, and die out shortly before reaching the regular rounded 

 simple margin. The last pair of pleurae is indistinct. 



Dimensions. — 



Length . . . . . 2'5 mm. 



Width . . . . . 2-0 „ 



Remarks. — The original specimen belonging to this species, which Nicholson 

 and Etheridge (pp. cit.) figured and described as " IJionide ? sp. ind." was 

 imperfect, for it lacked the marginal portion of the pygidium, which is now known 

 to be spinose. It is by means of the recently obtained material in Mrs. Gray's 

 collection from the original locality, Whitehouse Bay, that I am able to give the 

 above fuller and more accurate description of this peculiar form. Unluckily the 

 pygidia are always found detached, and the head and thorax of this interesting 

 trilobite are completely unknown. The true generic position of this curious 

 pygidium is uncertain, but there does not seem to be any reason for assigning it 

 to the genus Dionide. The only genus which has somewhat similar characters is 

 Lichapyge, 1 and this agrees in the triangular conical axis of few rings with a 

 narrow ridge reaching to the margin, and the anterior pairs of grooved pleurae 

 ending freely in spines on the margin, while the posterior ones end within it. The 

 only two species which appear to have been described as belonging to this genus 

 are L. primula, Barr., 2 from the Leimnitz beds of Hof, and L. cuspidata, Call. 

 (op. cit.), from the Shineton Shales of Shropshire. Both of these differ in having 

 only two pairs of pleurae with free extremities, and in having the posterior pleurae 

 very ill-defined. But in spite of these differences it seems better to associate 

 this Girvan form with this genus rather than with any other which has been 

 described. 



Collection.— Mrs. Gray (f. M.). 



Horizon and Locality. — Whitehouse Group (M. Bala) : Whitehouse Bay. 



1 Callaway, ' Quart. Jouru. Geol. Soc.,' vol. xxxiv (1877), p. 667, pi. xx, fig. 8; Liuuarssou, ' Geol. 

 Mag.' [2], vol. v (1878), p. 188. 



2 Barraude, ' Neues Jahrb. f. Miu., etc.' (1868), p. 679, fig. 34; Gumbel, ' Geogu. Beschr. Kim. 

 Bayern,' vol. ii (1879), p. 439, fig. 7. 



