8 DEVONIAN FAUNA. 



genus is peculiarly distinctive. Including its subgenera, it contains nearly 100 

 species, and extends from the top of the Cambrian to the Middle Devonian. 



1. Cheieurus Pbngellii, Whidborne. PI. I, figs. 10 — 13, 15, 16. 



1841. Caltmene Stebnbergii, Phil. (Not Boeck nor Minister.) Pal. Foss., p. 



128, pi. lvi, fig. 247. 

 1853. Cheirttbus articulatus, Salter. Geol. Surv., dec. 7, pi. i, Art. 1, p. 10. 

 1864. — — — Mon. Brit. Tril., p. 61, pi. vi, figs. 7, 8. 



1885. — gibbtjs, Rieman. (Pars.) Neues Jahrb., pt. 3, Beil.-Band, 



p. 147. 

 _ 1886. — — Barrois. (Pars.) Ann. Soc. Geol. du Nord, vol. 



xiii, p. 172. 



1888. — articulatus, Eth. Brit. Foss., pt. 1, p. 144. 



1889. — Pengellii, Whidb. Geol. Mag., dec. iii, vol. vi, p. 29. 



Description. — Head large, somewhat convex, rather elongate, semioval. Glabella 

 subquadrilateral, rather flattened, wider in front, sides diverging at an angle of about 

 18°, straight in profile. Front lobe short, depressed, wider than the others, the 

 segment of a sphere ; upper lobe straight, narrow ; second lobe expanding into an 

 escutcheon in the middle ; basal lobes triangular, with apices vis-a-vis, and about 

 one-fifth the width of the glabella asunder. Neck-lobe narrow, expanding upwards in 

 the centre. Furrows quite crossing the glabella, broad and distinct, and of uniform 

 depth both on the glabella and round the cheeks. Border covered and hidden by 

 the frontal lobe, forming a curve greater than a semicircle, met at the posterior 

 angle by the hind border of the cheeks, which runs straight across from the neck- 

 lobe, and terminated by a short stout spine tending rather outwards and downwards. 

 Cheeks flatly convex, bordered by steep furrows. Eye situated centrally in the 

 anterior part of the cheek. Facial suture cutting the border close beside the frontal 

 lobe, running straight down to the eye, and turning horizontally outwards to cut 

 the side border at a short distance above the angle. Surface of the glabella and 

 border bearing small, distant, sharp pustules ; cheek covered with larger close 

 pustules and punctations ; furrows smooth. 



Hypostome large, flatfish , convex, consisting of an ovoid central portion with a 

 lunate constriction separating its smaller end, and surrounded anteriorly by a very 

 narrow flat ring, expanding into sharply pointed triangles at the side. The 

 posterior half bounded by an elevated rounded border, having straight oblique 

 sides, and being squared and bevelled behind. Surface with numerous fine and 

 irregular granules. 



Tail convex, small, short. Axis elevated, conical, of about five segments; 

 limb with three or four large, rounded, bifurcated (?) ribs reaching to the border. 



