6 F. R. Coiqwr Reed — Undescribed Trilohitcs. 



marginal furrow of the Lead-shield by the lateral projections of the 

 median lobe. 



Middle lateral lobes subquadrate in shape, small and indistinctly 

 defined, being marked off in front from the anterior lobes by a very 

 faint depression sweeping round the hinder end of the latter lobes 

 and representing the middle lateral furrows. They are still more 

 indistinctly marked oif posteriorly from the basal lobes by weak 

 grooves, while their outer sides are defined by the faint axal furrows 

 and their inner sides by the continuation of the anterior lateral 

 furrows to the occipital segment. 



Basal lobes likewise weakly marked off from the rest of the 

 glabella and fixed cheeks, but relatively large, being nearly the size 

 of the middle lobes ; subrhomboidal rather than triangular in shape. 

 owing to the basal (posterior lateral) furrow starting, not from the 

 level of the occipital furrow but a little way in advance of it. 

 The posterior side of the basal lobes is marked off from the occipital 

 segment by the strong deep occipital furrow. 



Occipital ring flattened and very broad in the middle behind the 

 straight portion of the occipital furrow at the base of the median 

 lobe of the glabella, but with its lateral portions only about half 

 the width, and bent backwards behind the basal lobes. 



Axal furrows strongly marked only along the outer side of the 

 anterior end of the anterior lateral lobes, being posteriorly very 

 weak, as above mentioned. Behind the jDoint where they pass into 

 the marginal furrow which bounds the glabella in front they arch 

 outwards, curving round inwards posteriorly as they define the 

 anterior lateral lobes, to the base of which they nearly extend with 

 a deeply impressed course. Here the middle lateral furrows pass 

 imperceptibly into them. Behind this point the axal furrows 

 become very weak, and curve outwards along the outer side of the 

 middle and basal lobes to end in the occipital furrow. 



Anterior lateral furrows arise far forwards, curving round the broad 

 anterior end of the anterior lateral lobes, and then run with nearly 

 a straight course backwards along the inner side of these lobes, 

 slightly converging. At the posterior end of the latter each furrow 

 bends a little outwards to end in a small pit from which the middle 

 furrow starts. About half-way along the inner side of these anterior 

 lobes there is a slight outward kink in these anterior furrows, from 

 which a faint groove runs outwai'ds a little distance across the lobe, 

 such as has been noticed in Lichas ornatiis (Angelin),^ Lichas 

 anglicus (Beyr.), and other species. Behind the pits at the base of 

 the anterior lobes the anterior lateral furrows are traceable as faint 

 slightly divergent grooves (especially clear in the Fletcher specimen),, 

 which finally meet the occipital furrow at the inner posterior angle 

 of the basal lobes. 



Middle lateral furrows weak and short, starting from the pit on 

 the anterior furrows and curving round the base of the anterior 

 lobes to merge imperceptibly into the stronger axal furrows. 



1 Schmidt: Rev. Ostbalt. Silur. Trilob., Abth. ii (18S5), p. 109, t. vi, fig. 18^. 



