Vol. 52.] FAUNA OF THE KEISLET LIMESTONE. 429 



( = median) and anterior side-lobes each have a gentle independent 

 convexity of their own, but are somewhat flattened towards their 

 posterior ends. The middle and posterior side -lobes are flattened, 

 and do not rise above the common flattened surface of the posterior 

 half of the glabella. The cheeks curve down on each side with a 

 slight convexity of their own. 



A front view of the head-shield shows a gentle median upward 

 curve in the anterior edge forming a shallow bay, as in L. verrucosus, 

 Eichw. A narrow rounded border runs round the anterior margin 

 and is separated from the glabella by a shallow marginal furrow 

 passing laterally into the axal furrows. The latter, and all the 

 glabellar furrows, are well marked and of equal depth. 



The anterior glabellar side-furrows curve at first strongly inward, 

 but then run backward with a convergence of about 30° for more 

 than two-thirds the length of the glabella ; then they bend sharply 

 outward and forward at an angle of 60° to their former course to 

 form the incomplete middle side-furrows. These middle side- 

 furrows become suddenly faint about the middle of the base of 

 the anterior glabellar side-lobes, but are traceable into the axal 

 furrows. The posterior side-furrows are short and straight, and 

 form the direct lateral continuation of the straight median portion 

 of the neck-furrow, so that the glabella here appears crossed by a 

 single straight horizontal furrow, as in L. verrucosus, Eichw. This 

 horizontal furrow meets the axal furrows at right angles. The 

 neck-furrow on each side of the point of union with the posterior 

 side-furrows of the glabella bends sharply backward, so as to define 

 the basal glabellar lobe. 



The axal furrows start from the point of junction of the marginal 

 and anterior side-furrows, and a small pit is here situated. Erom 

 this pit the axal furrows run backward, curving outward in a 

 convex bow at the point where the ' eye-furrow ' branches off. 

 Thence they curve inward with an uniform gentle concavity, and 

 thus reach the neck-furrow ; but opposite the middle and basal 

 glabellar lobes their curve is slightly distorted and pushed outward. 



The frontal or median lobe of the glabella, from its front end to 

 the level of the middle side-furrow, reaches over two-thirds the 

 length of the head-shield. It has a marked convexity of its own, 

 particularly strong in its front part. The anterior downward slope 

 of its front end commences about halfway between the neck-furrow 

 and the anterior margin. The width of its front end is nearly three 

 times as great as the width of its posterior end at the level of the 

 middle side-furrows. The anterior lateral angles of this median 

 or frontal lobe are bluntly pointed, and overhang the anterior side- 

 lobes to half their width. 



The anterior side-lobes are roughly elliptical in shape, but their 

 ends are somewhat pointed. The middle side-lobes have a sub- 

 quadrate appearance, owing to their posterior outer angle being a 

 right angle and the third side-furrow being straight. They are 

 not marked off from the middle portion of the glabella either by 

 a furrow or by possessing an independent convexity. They are 



