10 DEVONIAN FAUNA. 



that the two latter are distinct ; and, moreover, Minister's figure of Ch. articulata is 

 much more like the German, than the English fossil. From the latter it differs 

 in the much greater length of the frontal lobe, the width of the glabella and the 

 angle of its sides, the absence of cheek-spines, and other features. After a very 

 careful comparison of it, Mr. T. Roberts agrees with me that in view of these 

 differences it is best to regard it as distinct, and to adopt the alternative name 

 which Salter suggested {op. cit., p. 62), and this I have the more pleasure in doing, 

 as it is after my old and honoured friend Mr. Pengelly, F.R.S., of Torquay. 



When, however, we come to compare this with the Bohemian species, we find 

 much greater grounds for hesitation. To two of these, Ch. Sternbergii 1 (Boeck) 

 and Ch. gibbus, Beyr., 2 it bears a very close likeness. Of these species there are 

 fine examples in the British Museum, and a careful examination of them, and of 

 Barrande's figures, shows that it stands exactly midway between. Ch. gibbus 

 is a much narrower and more convex form, and has a much more distinctive 

 appearance when judged from the whole fossil than from the head alone. In it 

 the frontal lobe is very large and prominent, and consequently the profile of 

 the glabella is concave instead of as in ours, roughly speaking, straight. The 

 cheeks are also decidedly shorter and narrower. Ch. Sternbergii, on the other 

 hand, has the frontal lobe still shorter and more depressed than Ch. Pengellii, 

 and the profile of the glabella is definitely convex instead of straight. The eyes 

 also appear to be situated further from the glabella, the furrows of the glabella 

 are more oblique and shallower in the centre, the apices of the basal lobes come 

 much closer to each other, the cheeks appear to be decidedly wider and less 

 convex, and the margins of the hypostome are smooth. The tail appears shorter 

 but generally very like the English fossil, which differs distinctly from that of 

 Ch. gibbus. Thus, though it is quite possible that Ch. Pengellii may ultimately 

 prove to be only a local variation of Ch. Sternbergii, the points of difference are 

 so numerous and persistent that it could not safely be classed with it at present. 



Ch. Quenstedti, 5 Barr., differs in having more oblique and less continuous 

 furrows, and in the shape of the second lobe of the glabella and of the tail. 

 Ch. myops, F. A. Romer, 4 has a much more triangulated head, a much squarer 

 glabella, and a smaller eye. Its hypostome also seems differently shaped 

 Ch. gibbus, as figured by Sandberger, also differs in several respects ; the front 

 lobe is longer, the sides of the glabella more oblique, the lobes of the glabella 

 more arched, and the basal lobes much nearer together. 



1 1852, Barr., ' Syst. Sil.,' vol. i, p. 795, pi. xli, figs. 29— 39, and Supplement, p. 94, pi. xii, 

 figs. 8—15, Stages E— H. 



2 1852, Barr., 'Syst. Sil.,' vol. i, p. 792, pi. xl, figs. 35—39; pi. xli, figs. 17—27; and pi. xlii, 

 figs. 12—15, Stages E and Gk 



3 1852, Barr., ' Syst. Sil.,' vol. i, p. 790, pi. xl, fig. 13 ; and pi. xlii, figs. 2, 3, 4, Et. E. 



4 1850, F. A. Eom., ' Beitr.,' pt. 1, p. 65, pi. x, fig. 8 ; and pt. 3, p. 24, pi. 20, fig. G. 



