fiY JOHN MITCHELL. 477 



men was not quite complete, being minus part of the right front 

 quarter of the cephalon. 



This fossil agrees very closely with one described by De 

 Ivoninck from the Upper William River,* and determined by 

 him to be Grijfithides (Phillipsia) eichwaldi. 'Jhe total lengths 

 of the two fossils exactly agree, as also do the widths of the 

 thoraces; but there are some discrepancies in the dimensions of 

 the separate parts. De Koninck gives 10 mm. and 8 mm., re- 

 spectively, for thorax and pygidium of his specimen; whilst 9mm. 

 is the length of each of these parts in the specimen under 

 review. The two hav^e nearly the same number of annulations 

 in the pygidial axis, and probably the same number of pleural 

 ribs, a similar wide pygidial border: also the same relative 

 length to width of their pygidia, and an identical frontal pro- 

 jection of the glabella on to the border. In the characters of 

 granulation and of thoraces and pleural ribs of the pygidia, thev 

 also agree. If, at this, the discussion of their relationship 

 stopped, the identity of the two would have to be accepted as 

 conclusive, as I believe it actually to be. But against these 

 agreements have to be placed some important differences, which 

 make their specific identity difHcult to reconcile. For instance, 

 T>e Ivoninck states that his specimen has only eight thoiacic 

 segments, that tlie anterior annulation of the thoracic axis has a 

 widthf of 3 mm., and not one of the annulations has a width 

 less than 1 mm. The present specimen has the normal nine 

 somites, and the widest annulation of the thoracic axis does not 

 exceed 1 mm. De Konincks figure of his specimen shows it to 

 have had a \'ery globular frontal glabellar lobe, and, in this, differs 

 from the one above described. Again, De Konincks text does 

 not agree with his illustiation. The former indicates his speci- 

 nien to have eight thoracic somites, and the pleural lobes to have 

 a width equal to that of the thoiacic axis; but his figure shows 

 nine somites, and pleural lobes much narrower than the axis. 

 These important discrepancies make it impossible to accept his 



" Foss. Pal. Nouv. (dalles du Sud, Pt. i., 1870, pp.278-9, PI. xxiv., tig.8. 

 I The writer assumes the width of tlie axial rings to be their measure- 

 ment alonj.; the lonifjtudinal line of the axis. 



