6 F. R. Cowper Reed — Some Wenlock Species of Lichas. 



margin furnished with strong short outwardly projecting spine^ 

 curving slightly backwards. 



Head-shield iu all parts (including spines) ornamented with large 

 tubercles, not closely set, with smaller ones interspersed. 



Thorax composed of eleven segments. Axis moderately convex, 

 nearly as wide as pleural portions, cylindrical for first six or 

 seven rings, then tapering gradually backwards to pygidium. Axal 

 furrows well-marked. Axial rings narrow, rounded, with narrow 

 articulating band. 



Pleura narrow, rounded, cylindrical, with free pointed extremities ;. 

 horizontally extended to fulcrum, which is situated at about half 

 their length, then bent downwards and slightly backwards. Narrow 

 flattened band on front edge. Each thoracic segment bears a single- 

 row of a few large equally-spaced tubercles. 



Pygidium broadly parabolic, usually slightly broader than long. 

 Axis convex, subcylindrical or slightly tapering, bluntly rounded at 

 posterior end ; extends about two-thirds the length of pygidium, 

 and occupies about the middle third of width. One strong complete 

 axial ring at front end with narrow articulating band on front edge, 

 followed by 3-5 narrow transverse rows of tubercles in middJe 

 portion of axis ; the first one or two rows are separated by mor& 

 or less distinct furrows. Posterior end of axis abrupt, blunt, not 

 circumscribed by furrow, but continued posteriorly by narrow, 

 depressed, tapering post-axial median piece, which becomes parallel- 

 sided and extends to posterior border between third pair of marginal 

 spines. 



Lateral lobes flattened, slightly bent down, with three pairs of 

 large spines projecting beyond the margin and numerous minute 

 spinules or prickles. Two pairs of well-defined pleurae curving 

 backwards ; each pleura marked by median furrow dividing it into 

 two unequal portions, of which the posterior is the narrower and 

 more elevated. Each pleura is produced beyond pygidial margin 

 into short free point, forming thus the two anterior pairs of marginal 

 spines, which also bear small lateral prickles (only occasionally 

 preserved). Pleurje separated by well-marked interpleural furrows 

 curving backwards, of which the first makes an angle of about 30°^ 

 with the front margin, and the second makes an angle of about 

 60°-70° with the same. Between the second pleura3 and the- 

 post-axial piece is a triangular', irregularly tuberculated area on each 

 side with no furrow upon it. The posterior pair of spines are 

 approximate and directed straight backwards, and are generally 

 about equal in length to the second pair, from which they are- 

 removed by about twice the distance that they are from each other^ 



Measurebients. 



mm. 



Length of trilobite 21-0 



Length of head-shield 6-5 



"Width of head-shield (from tips of genal spines) 18-0 



Length of thorax 7*5 



Length of pygidium 7"0 



"Width of pygidium 9-0 



