12 TRILOBITES OF GIRVAN. 



Family Olenid^e. 

 Oenus REMOPLEURIDES, Portlock. 

 Remopleurides nicholsoni, sp. nov. Plate II, figs. 3—9. 



1903. Remopleurides colbii, Reed (non Portlock), op. cit., pt. i, p. 36, pi. v, figs. 17 a, b. 



Specific Characters. — Head-shield sub-semicircular. Glabella very slightly 

 convex, transversely sub-elliptical, widest near base ; anterior tongue strongly 

 arched down and more than one-third the length of glabella, parallel-sided, about 

 half as wide as glabella, with front end subtruncate and furnished with narrow 

 band. Two pairs of lateral furroAvs present, fine, faintly impressed, gently arched. 

 Fixed cheeks represented by narrow flattened band, widening a little at base of 

 glabella (which is here constricted), marked off l)y strong furrow. Meso-occipital 

 ring flattened, narrowing on each side outside base of glabella, finely serrated on 

 posterior edge and crossed from side to side by very delicate strijB. Facial 

 sutures bend out sharply at base, cutting posterior margin at acute angle. Free 

 cheeks triangular, with short nearly straight posterior margin meeting lateral 

 margin at right angles without a true genal spine. Pleuro-occipital ring broad, 

 marked off by strong furrow, ending abruptly against lateral margin of cheek. 

 Cheek-spine arising in front of true genal angle from side of cheek, slender, 

 tapering, gently curved, produced back at acute angle to lateral margin behind its 

 base so as to form a subgenal notch. Eye large, vertical, band-like, widening a little 

 anteriorly to tongue of glabella, composed of numerous (two hundred or more) 

 vertical rows of alternating small closely set lenses, thirty to forty lenses in a row ; 

 narrow basal rim to eye present, defined above and below by sharp groove. 



Thorax composed of eleven body rings, gradually and regularly decreasing in 

 size posteriorly. Axis conical, tapering to pygidium to less than half its anterior 

 width, moderately convex, anteriorly about half width of thorax, with the rings 

 ornamented by closely set slightly sin uous~ striae parallel to anterior edge, and by 

 small serrations on posterior edge. On ninth ring stout median spine (length 

 unknown) projects upwards and backwards. 



PleuraB regularly decreasing in size posteriorly, possessing the characters of 

 Ii. colbii, except that they are ornamented along their length by fine subparallel 

 strias like those on axial rings. 



Pygidium oblong, with posterior edge cut into four teeth, of which the two 

 outer ones are the shorter. Axis short, very broadly conical, well-defined, convex, 

 about half the total length of pygidium and about two-thirds its width ; composed 

 of two segments, the first widens suddenly on each side so as to overlap the second ; 

 the second segment composed of a pair of contiguous oval swellings diverging 



