242 F. R. Coivper Reed — On Phacops (Chasmops) Marri. 



Length of head 1"35 inch 



Length of glabella from neck-furrow to anterior end 1-1 ,, 



"Width of broadest part of glabella, i.«. across frontal lobe 1-1 ,, 



Width of base of glabella 0-35 ,, 



Length of the 1st or " cat's ear" lobe, measured along its outer side ... 0-675 ,, 

 Width of right cheek measured along the neck-furrow from the axial 



furrow to the outer margin 0-9 ,, 



Length of eye 0-375 ,, 



Width of eye 0-175 ,, 



Length of channel round eye 0-5 ,, 



Width of ditto 0-225 ,, 



Width (average) of thoracic axis 0-5 ,, 



Length (average) of pleura 0-8 ,, 



Width (average) of ditto 0-2 ,, 



The accompanying description refers to the crushed and distorted 

 specimen figured. (A summary of the chief characters of the form 

 with the proportions, which it must have possessed prior to the 

 distortion, is given subsequently.) 



The outline of the head is parabolic ; the anterior end appears to 

 be obtusely pointed in front of the glabella. The glabella is much 

 dilated in front, and the sides converge at an angle of about 40°, 

 but before distortion this angle must have been about 60°, and the 

 outline of the head must have been semicircular. 



The frontal and first lobes of the glabella are well marked off by 

 deep furrows. The frontal or forehead lobe is transverse, the width 

 1^ times the length, but originally it must have been about twice as 

 wide as long ; the anterior border is a gentle convex-forward curve ; 

 the lateral angles of this lobe are rounded-truncate, and overhang 

 the eyes completely, projecting beyond the straight outer side of the 

 " cat's ear " lobes. 



A Yishnu-like mark formed by two converging rows of large 

 puncta, which may represent the position of frontal glands, extends 

 two-thirds down the lobe from the anterior border. 



The triangular " cat's ear " or first side lobes extend fully two- 

 thirds of the side of the glabella, reaching nearly from the neck- 

 furrow to a point in front of the eye ; each of these lobes stretches 

 nearly one-third of the way across the glabella. The largest angle 

 of each is about 110° and points inwards, but before distortion must 

 have approached a right angle. The anterior bounding furrow is 

 rather sinuous, but the posterior one is straight. 



In the triangular portion of the glabella left between these large 

 embracing lobes, the second or middle lobes are represented by 

 small, very faintly indicated, subcircular elevations, more clearly 

 defined in front than behind, and only perceptible in the impression. 

 The basal or third lobes are larger and transverse, but are poorly 

 defined, and together with the middle ones ai'e completely embraced 

 laterally by the large first lobes. (This feature also is shown better 

 in the impression than in the cast.) 



The glabella as a whole is not particularly inflated, and, in fact, 

 is not so high as the inner portions of the cheeks ; but this is 

 probably due in the main to the crushing to which it has been 

 subjected. 



