BRITISH FOSSILS. 



3 



directed obliquely downwards and joining the neck furrow before 

 reaching the middle ; it thus encloses a spherical triangle as a basal 

 lobe. In older specimens this lobe is somewhat squarer, and the 

 fiirrow more curved. The other furrows curve but little downward, 

 and are variable in length, but usually extend more than one 

 third across the glabella on each side. The furrows on the glabella, 

 as well as the axal farrows, are sharp, but not broad or deep ex- 

 teriorly, although they are so on casts of the inner surface. Fore- 

 head lobe of moderate size, half as long as the entire glabella, and 

 on the sides overhanging the other lobes, — in front it is somewhat 

 produced and occupies all the margin. The glabella is neither 

 gibbous nor depressed, a line taken from the front edge to the neck 

 farrow presenting a regular and gentle convexity. Cheeks subtri- 

 angular, not so wide as long, with a broadish margin distinctly sepa- 

 rated by a farrow, which meets the strong straight neck furrow at 

 the posterior angles ; these angles are spinous, the spine short and 

 directed backwards. The eye is placed more than half-way up the 

 cheek, and not close to the glabella, it is opposite the middle fur- 

 row,* and is rather small, supported by a raised rim below ; the 

 eyelid is narrow and indented, — the lentiferous surface (ng. 7) very 

 convex, supine, and covered with minute, closely set, convex facets 

 with no spaces between them. Our figure, 7*, represents each facet 

 as with a minute pit upon it, but this is due to wear, (at a lens is 

 seen in the natural condition). Above the eye the facial suture takes 

 a sigmoid curve, and cuts the margin exactly where the axal furrow 

 ends on it ; below the eye it turns directly downwards to the smooth 

 border, which it cuts considerably in advance of the posterior angle, 

 and in an oblique direction, so that it reaches farther back on the 

 lower side than on the upper. We do not know the course of the 

 suture in front, — ^it is probably direct across, beneath the front 

 margin, leaving the cheeks united there, as in Sphmrexochus, next 

 described. The surface of the glabella is sparsely covered with 

 small granules (fig. 1*, a) ; the cheeks are largely scrobiculate, (6, c), 

 and the wings or free cheeks have their border smooth and only 

 scabrous on its outer edge ; they sometimes, as fig. 10, dilate a little 

 in advance of the facial suture. Hypostome (figs. 11 to 15) la.rge, 

 ovate, oblong, very convex, its length one fourth more than the 

 width, but in appearance more ; broadest near the base of insertion, 

 from which the central convexity rises immediately and reaches 



* Loven calls tlie upper furrow '■^ frontalis and the middle one " ocularis" and, though 

 not always strictly correct, it would be a very useful designation. We have employed il 

 above in the diagnosis. 



