114 TRILOBITES OF GIRVAN. 



Remarks. — The imperfect pygidium figured by Nicholson and Etheridge (op. cit.) 

 from Mulloch Hill as " Acidaspis sp." may without much doubt be referred to Mr. 

 Lake's species, A. dejlexa. The woodcut given by them is misleading, for the 

 second pair of spines are almost parallel and do not curve inwards as there indicated. 



The species is also represented in Mrs. Gray's collection by several nearly 

 complete specimens from the same locality. The pygidia have the first pair of 

 spines rather more developed than in Mr. Lake's type-specimen, but he agrees with 

 me that these Girvan specimens are referable to A. dejlexa. 



Collections. — Mrs. Gray (f. M.) : Woodwardian [Sedgwick] Museum. 



Horizon and Locality. — Mulloch Hill Group (L. Llandovery): Rough Neuk ; 

 Mulloch Hill. 



5. Acidaspis grayae, Etheridge, jun., 1878. Plate XV, figs. 1G— 18 ; Plate XVI, 



figs. ] , 2. 



1878. Acidaspis grayae, Etheridge, juu., Proc. Koy. Phys. Soc. Edinb., vol. it, p. 170, pi. ii, 



figs. 6-8. 

 1878. Acidaspis grayse, Nicholson and Etheridge, Mon. Silur. Foss. Girvan, fasc. i, p. 126, pi. vin, 



fig. 26 ; pi. ix, figs. 1 — 7, and p. 129, fig. 7 b. 

 ? 1878. Acidaspis lalage, Nicholson and Etheridge (e. p.), ibid., pi. viii, figs. 18, 19 (non figs. 17, 20 — 22). 

 1899. Acidaspis gray*, Mem. Geol. Surv., Silur. Kocks Brit., vol. i, Scotland, pp. 509, 671, 688. 



Specific Characters. — General form oval, depressed. 



Head-shield sub-semicircular, rather flattened in front. Glabella convex, para- 

 bolic, broadest behind. Lateral lobes imperfectly known owing to bad preservation 

 of type, but apparently three pairs are present ; anterior pair mere nodules ; second 

 pair round; third pair elongate, oval; all circumscribed completely and separate; 

 central lobe cylindrical. Occipital ring very broad, projecting posteriorly, marked 

 off from central lobe of glabella by wide shallow furrow. Occipital lobes narrow, 

 oblique (as in A. lalage, q. v.). Fixed cheeks triangular, swollen, separated from 

 glabella by deep axial furrows. Eye-ridge running outwards from anterior end 

 of glabella to eye, curved, rounded, narrow, broadening posteriorly. Eve small, 

 (listni it from axial furrow about half (?) width of glabella, and situated opposite 

 middle of glabella. Free cheek with smooth narrow lateral border armed with 

 aboul 1 1< radiating spines decreasing in length anteriorly. Genal angle furnished 

 with long curved spine, extending about three fourths the length of the thorax. 

 Surface of head-shield covered with minute tubercles, somewhat scattered. 



Thorax of ton segments. Axis narrow, convex, prominent, sub-cylindrical, 

 tapering a little to pygidium; about one fourth the width of thorax; axial rings 

 with obscure lateral swellings. Pleurae straight, horizontally extended, with broad 

 nearly median longitudinal groove, bordered by narrow rounded elevated margins, 



