LICHAS (AMPHILICHAS) ARDMILLANENSIS. 29 



Thorax of eleven segments. Axis broad, nearly as wide as pleural portions, 

 subcjlindrical, tapering very slowly behind seventh or eighth ring. Pleurae 

 narrow, arched back and downwards beyond weak fulcrum situated at less 

 than half their length, divided longitudinally by weak submedian slightly diagonal 

 furrow. Surface of thorax granulated and with a few scattered tubercles. 



Pygidium transverse ; axis cylindrical, three-fourths its length, showing one 

 ring at front end and faint traces of others, with narrow pointed post-axial 

 ridge continued to margin. Lateral lobes formed by three pairs of pleurse ending 

 freely on margin ; first and second pairs of pleurge lanceolate, narrow, arched back 

 gently, each with submedian furrow and pointed extremity freely projecting ; first 

 pair with ends reaching back as far as tip of axis ; second pair with ends reaching 

 l)ack a little behind tips of third pair ; third pair large, subtriangular, broadly 

 bifurcate, each pleura ending on margin in two blunt short points, separated by post- 

 axial ridge, and with a small median acute re-entrant angle between their closely 

 placed inner points. Surface of pygidium granulated and with scattered tubercles. 

 Dimensions. — 



Length of head-shield . . . 7'5 mm. 



Width of „ . . . . 20-8 „ 



Length of thorax .... 9*5 ,, 

 „ of pygidium .... 7"3 ,, 

 Width of „ . . . . 12-2 „ 



Bemarlcs. — The difference between this species and L. geikiei, Eth. and Nich., 

 lies in the complete fusion of the fixed cheeks with the fourth lateral lobes of the 

 glabella of the former, in the more cylindrical median lobe of the latter, and 

 especially in the characters of the pygidium, the axis of L. geikiei having more 

 annulations and the last pair of pleurae being not bifurcated ; the ornamentation is 

 also distinct, as one small complete individual of L. geikiei shows. An isolated 

 pygidium attributed to L. geikiei has been previously described and figured by me,^ 

 but one has now been found in attachment to a perfect thorax and head-shield. 

 The condition of the glabella in L. macculJoclii and its fusion posteriorly with the 

 fixed cheeks, resemble L. haueri, Barrande,^ while its pygidium is much like that 

 one compared by me to L. ivesenbergensis, Schmidt,^ from the Balclatchie Group. 



Horizon and Locality. — Starfish Bed, Drummuck Group (U. Bala) : Thraive 

 Glen. 



Lichas (Amphilichas) ardmillanensis, sp. nov. Plate V, fig. 1. 



Specific Characters. — Cranidium weakly convex from side to side, not bent 

 down in front. Glabella sub-oblong, slightly contracted behind middle, expanding 



^ Eeed, op. cit., pt. iii, p. 96, pi. xiv, fig. 1. 



2 Barrande, ' Syst. Silur. Boheine,' p. 604, pi. xxviii, figs. 38 — 40. 



■' Reed, op, cit., pt. ii, p. 98, pi. xiv, fig. 2, 



