30 TRILOBITES OF GIRVAN. 



a little towards front and base, composed of a median lobe and a pair of tri- 

 composite lateral lobes. Median lobe transversely clavate, expanded anteriorly, 

 with prominent subconical projection in middle ; lateral portions narrow and over- 

 hanging lateral lobes for nearly their f idl width ; neck of median lobe long, narrow- 

 ing posteriorly at half its length to less than a quarter the width of anterior clavate 

 portion, then expanding again to occipital furrow to about one-third the basal 

 width of whole glabella. Lateral lobes tri-composite, with base resting on occipital 

 furrow, subreniform, elongated, rounded and bent down at front end, curving 

 outwards posteriorly and obtusely pointed at outer posterior angle, widest towards 

 front ; small notch present on inner side at one-third their length from base. 

 First lateral furrows well marked, continuous from front of lateral lobes to 

 occipital furrow, nearly horizontal at anterior end of lateral lobes, then curving 

 backwards with slight convergence to about half their length, then bending gently 

 outwards to the notch on inner side of lateral lobes, then diverging outwards to 

 meet occipital furrow at about 75°. 



Axial furrows strong, continuous all round glabella, arching outwards at first 

 from front end, then bending inwards slightly to constrict glabella behind middle, 

 then bending outwards slightly to posterior margin. Meso-occipital furrow strong, 

 straight and horizontal behind median lobe, sloping backwards on each side behind 

 lateral lobes. Meso-occipital ring simple, rounded, narrowing behind lateral lobes. 

 Occipital lobes absent. Fixed cheeks small, bent down on each side ; eye-lobes semi- 

 circular, situated at level of notch on inner side of lateral lobes and close to axial 

 furrows. Surface of cranidium tuberculated, a few larger conspicuous tubercles 

 being irregularly distributed amongst numerous smaller ones of two or three sizes. 

 Dimensions. — 



Length of cranidium . . . 9v mm. 



,, of lateral lobes . . . 6*0 „ 



Maximum width of glabella across lateral lobes . 9"0 „ 



Minimum width of median lobe . . 1"8 „ 



Remarlis. — The shape and anterior projection of the median lobe of the glabella 

 recall species of Conollclias, but the general characters of the cranidium ally it to 

 L. hihernicns, PortL, and L. dalecarlicns, Ang.,^ from which, however, it is clearly 

 distinct in the shape of the median lobe, the course of the first lateral furrows and 

 the notched lateral lobes. 



Horizon and LocaUty. — Balclatchie Group (Llandeilo) : Ardmillan. 



Lichas (Amphilichas) hibernicus, Portlock. Plate V, fig. 2. 



1906. Lichas (AmpJiilichas) liihernicus, Portlock, Reed, op. cit., pt. iii, p. 106, pi. xv, figs. 1 — 3. 



A fine pygidium (24 mm. long) of this species from Ardmillan is deserving of 

 1 Sclimidt, ' Eev. Ostbalt. Silur.- Trilob.,' pt. ii (1885), p. 53, pi. vi, figs. 11—13. 



