ILL^NUS RICHARDSONI. 



25 



Horizon and Localities. — Balclatchie Glroup (Llandeilo) : Balclatchie ; Dow 

 Hill. 



Illaenus portlocki, Salter. 



1904. Illmnus portlocki, Salter, Reed, op. cit., pt. ii, p. Q7, pi. ix, figs. 14 — 16 ; pi. x, figs. 1,1a. 



There are many good examples of tlie pygidia belonging to this species and of 

 cranidia of the type referred to it which have been recently found by Mrs. Gray 

 in the Balclatchie Group of Balclatchie and Dow Hill. Previously it had only 

 been recognised in the Stinchar Limestone of Craighead. 



Illaenus richardsoni, sp. no v. 



Plate IV, figs. 4, 5. 



Specific Characters. — -Cranidium oblong, moderately convex from side to side, 

 arched down steeply and suddenly in front of glabella, anteriorly truncate. 



Glabella very broad, widest across middle, fully two-thirds the width of 

 cranidium, very short, less than one-third the length of cranidium, with slight 

 independent convexity and small median tubercle situated at half its length. 

 Fixed cheeks narrow ; eye-lobes large, semicircular, about one-fourth the width of 

 glabella and as long as glabella, nearly touching posterior margin of head-shield 

 behind. Axial furrows well marked, slightly sigmoidal, arching outwards in 

 middle. Facial sutures with anterior branches subparallel, directed at right 

 angles to anterior margin of head-shield, slightly bending inwards to eye-lobes ; 

 posterior branches very short, sharply bending out behind eyes to meet posterior 

 mars^in at an acute anofle. 

 Dimensio7is. — 



Length of glabella 



,, of preglabellar portion 

 Width of glabella at base . 



,, of cranidium across eye-lobes 

 ,, ,, at front end 



Beinarks. — The characteristic features of this species are the great width and 

 shortness of the glabella, the narrow cheeks, the large eyes set far back and the 

 parallelism of the facial sutures in front of the eyes. Perhaps it may be allied to 

 y. chiron, Holm.^ 



Horizon and Localities. — ^Balclatchie Group (Llandeilo) : Balclatchie and 

 Ardmillan. 



. 7-2 



mm. 



. 15-8 



J5 



. 14-0 



J5 



. 21-0 



5? 



. 17-0 



•, 



1 Holm, ' Sveusk. Artern. Illseniden ' (1883), p. 88, pi. iii, fig.«. 7—17. 



