1865.] SALTER — LIJSTGULA-FLAG FOSSILS. 479 



The cheeks are divisible into two portions, which must be separately- 

 described. The fixed cheeks are wide, nearly triangular, bounded at 

 the base by the posterior margin, and on the outer side by a broad 

 rim or margin, which continues of the same breadth all the way iip, 

 and is the upper covering of the eye*. Outside this the linear free 

 cheek is continued backwards by its strong margin to form the long 

 curved slender spines, whilst the limb is contracted and does not reach 

 to the posterior margin of the fixed cheek ; in consequence of this 

 contraction occurring about | of an inch above the line of the poste- 

 rior margin, the outer angle appears to be suddenly and abruptly 

 emarginate and to have two posterior angles. A rather narrower 

 border (eye-lobe) surrounds the fixed portion of the cheek, dividing it 

 from the outer, extending from opposite the frontal lobe of the glabella 

 to the posterior margin, and including within it a spherico-triangular 

 space. This surface is flattened, rugose-punctate, and rises into a 

 sharp narrow ridge on its inner border, from opposite the middle gla- 

 bella fm-row down to the neck furrow. The neck furrow is strong and 

 wide, and continuous at the outer angle with the equally strong furrow 

 which runs inside the strong border (eye-lobe) of the fixed cheek. 

 The facial suture cui-ves outwards and upwards above the eye, and 

 cuts across the outer margin ; also downwards and outwards below 

 the eye along the broad margin or eye-lobe of the fixed cheek to the 

 posterior border, terminating just above and to the outside of its short 

 acute angle. The outer cheeks are, as above said, long and narrow, 

 and terminate in the long tapering head spines, which, though mode- 

 rately wide at the base, are for the most part slender, and extend 

 backwards to opposite the ninth or tenth pleurse. The outer cheeks 

 are, moreover, very loosely attached to the head, and are very seldom 

 found in situ. 



The labrum is large, much compressed and expanded at the base ; 

 the apex truncate, wdth short spinous angles ; a deep sulcus runs 

 along the inner border of the apex, and a little within this on either 

 side a small tubercle is seen. (No perfect specimens of the labrum 

 have yet been found.) The thorax, comprising more than a half of 

 the whole length, has a broad axis consisting of 14 or more segments, 

 the upper seven or eight being wider than their pleiu'ae, including their 

 short spines, whilst the last three or four are from g to J- shorter than 

 their attached pleurae, the spines of which are greatly and suddenly 

 increased in size and length. The axis is gently raised above the 

 pleurae, and is separated from them by rather deep axial furrows ; 

 the segments of the axis curve slightly backwards, and have a strongly 

 sculptured surface. The pleurae are broad, much flattened, and 

 marked by a rather distinct lineation running parallel with the uj^per 

 and lower borders, grooved deeply and obliquely from their upper 

 inner angle to their outer margin at the base of the spines. The spines 



* This remarkable border, which at first sight appears so anomalous, running 

 across the cheek as if tliore wore two borders to it, is in reality the eye-lobe ! 

 The eye is thus of immoderate length. We have only lately seen it in the true 

 light ; and I find that Prof. Angelin has figured a very similar fossil under the 

 name of Faraduxides Loveni. It has a somewhat shorter eye. — J. W. S. 



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