BRONTEUS. 33 



generally very imperfect, and much obscured by distortion and the effects of 

 fossilization ; and, while the specimens of either part fall into distinct groups, it is 

 almost impossible to come to a satisfactory conclusion as to which of the two sets 

 should be correlated one with another. There is, moreover, considerable variability 

 among the individuals of each group. Neither is much help to be obtained from 

 the descriptions given by foreign authors. Except in the case of the Bohemian 

 species they have generally been described from the pygidia alone ; and endless 

 differences of opinion exist among the later writers as to the exact species 

 which were intended by the earlier. Under these circumstances the present 

 effort to define the English species must be considered to a great extent as only 

 tentative. There would be of course the opposite and much easier course of 

 regarding them simply as a single very variable species, but my strong impression 

 is that the species will ultimately prove to be numerous, and that the intricacy lies 

 rather in the poorness of the specimens than in the indistinctness of the species. 



1. Beonteus delicatus, Whidborne. PL III, figs. 13 — 15. 



1889. Beonteus delicatus, Whidb. Geol. Mag., dec. 3, vol. vi, p. 29. 



Description. — Head considerably longer than the width of the glabella, mode- 

 rately convex, rounded in front. Border small but stout, divided from the 

 glabella by a shallow linear groove, and marked by numerous transverse striae. 

 Glabella triangular, narrow behind, almost uniform in height till it curves rather 

 suddenly to the border ; bounded on each side by a rounded axal furrow, separating 

 it from the fixed cheeks, at first straight and then arching outwards, and with a small 

 pit nearly in its centre. The first frontal depression distinct, almost crossing the 

 glabella, parallel to the border, and distant from it about a quarter the length of 

 the head. Behind this the frontal and ocular furrows form a deep, smooth 

 triangle, including a lateral tubercle representing the upper lobe. Between the 

 apex of this and the first-mentioned furrow is another short depression not 

 reaching the margin. Basal furrow truncating the glabella, followed by a small 

 basal lobe, with a lateral prominence bearing a tubercle. Neck-lobe high and 

 arched. Surface of the glabella covered, except in the depressions, by fine irregular 

 transverse ridges, tending to become nodulose, especially behind. 



Tail rather short (?). Axis small, very tumid, subspherical, with no signs of 

 trilobation, and having minute lateral prolongations ; surrounded by a furrow. 

 Ribs fifteen ; the central one much larger than the rest, the lateral ribs slightly 

 increasing in width with their distance from the centre. Furrows about half the 

 width of the ribs, smooth. Limb rather concave near the margin. Axis and 

 ridges marked with a few very small raised spots. 



