42 TRILOBITES OF GIRVAN. 



owing to the ornamentation of the surface. The fourth pleuras have a straight 

 slender posterior ridge running close against the axis and continued beyond it 

 alongside the post-axial piece to end in a small free point on the margin. A few 

 scattered tubercles occur on the pleural ridges. The ornamentation of the lateral 

 lobes of the pygidium sufficiently distinguishes this Girvan form from the typical 

 C. hellatnla. 



Dimensions. — 



Length of pygidium . . . . 133 mm. 



„ of axis .... 9*2 ,, 



Width of pygidium .... 13'7 „ 

 5, of axis at front end . . . 4*6 ,, 



Horizon and Locality. — Balclatchie Group (Llandeilo) : Balclatchie. 



Cybele michelli, sp. nov. Plate VI 1, fig. 7. 



1906. Cybele cf. aspera, Linnarsson, Eeed, op. cit., pt. iii, p. 128, pi. xvi, figs. 12, 13. 

 ? — Cybele sp. b. (pars), Eeed, ibid., p. 180, pi. xvii, fig. 8 (tion 6, 7). 



Specific Characters. — Head-shield transversely semicircular, rather more than 

 twice as broad as long, slightly arched forwards on each side and in front of 

 glabella, convex, bent down strongly on each side and produced back to genal 

 angles ; cheeks swollen, much elevated, subconical, rising steeply from anterior 

 margin and axial furrows ; genal angles blunt ; upper edge of rostral shield 

 appearing on upper surface of head-shield and forming pre-glabellar border. 



Glabella subclavate, expanding a little in front of anterior lateral furrows, 

 convex, rounded, swollen, nearly touching anterior margin and encircled in front 

 by rostral suture with no distinct pre-glabellar band. Three pairs of lateral 

 furrows represented by short deep transverse pits not connected with axial 

 furrows, set at equal distances apart and successively increasing in size posteriorly ; 

 anterior pair situated rather in front of middle of glabella. 



Meso-occipital ring rounded, widest in middle, marked off from glabella by 

 furrow strongly arched forwards in middle, with a deep pit in it on each side 

 similar to and in a line with lateral pits on glabella. 



Rostral shield with upper rounded smooth edge forming a narrow pre-glabellar 

 marginal border, lying between the connecting sutures and in front of the rostral 

 suture on upper surface of head-shield, about one-third the width of glabella. 



Axial furrows slightly divergent anteriorly, with large round deep pit situated 

 on each side of frontal lobe of glabella at the point where they fork, the outer 

 stronger branch bending out and continued into marginal furrow of cheek, the 

 inner weaker branch continued round front end of glabella, thus between them 

 separating off subtriangular swollen anterior end of fixed cheek. 



A 



