10 



BRITISH FOSSILS. 



bearing very forward eyes. They are placed on the most prominent 

 part of the cheeks, opposite the front of the glabella, and about 

 midway from it. The fixed cheek is wider than the glabella, but 

 the free cheek is not so wide, and much resembles that of 0. humilis. 

 And the facial suture, as in that species, is nearly vertical below 

 the eye as well as above it. 



The head-spine does not in this species start from nearly the 

 base, but quite up in the middle of the free cheek. It is only slightly 

 curved ; but arising from so unusual a position, it has a most odd 

 appearance. It reaches to the seventh thorax ring. 



The thorax-rings are much wider than the head, and remarkably 

 straight across. The axis is not above one-third the width of the 

 straight pleurae, which are even a little curved upward, and grooved 

 throughout ; they bear a straight spine, directed obliquely back- 

 wards, and longer in the hinder segments. We only know seven 

 rings ; there must have been several more. 



Mr. Turner, schoolmaster at Pauntley, Gloucestershire, was the 

 discoverer of this curious species, and sent it to the Rev. W. Symonds. 

 It has since occurred in greater plenty. Mr. Edgell has perfect 

 heads and several caudal portions. The Rev. T. B. Brodie has an 

 excellent specimen. 



Locality. — With the preceding. 



The group of species last described rather fully illustrate the 

 curious sub-genus Sphcerophthalmus, and show how wide in these 

 ancient genera the limits of variation are in a single group. As we 

 ascend in the geological scale, the law of variation becomes more 

 restricted, and characters which are of family value in the more 

 advanced groups scarcely afford generic distinctions in some of the 

 more ancient and less highly organized ones. 



The Olenidm and the Asaphidm have both of them wide limits, 

 and it may be possible bye and bye to subdivide them. 



Locality and Geol. Position. — Upper Lingula Flags, White- 

 leaved Oak, Malvern. 



Figs. 15, 16, 17. 



I have figured the Swedish O. spinulosus (fig. 16,) to give the British student an idea of 

 what form to look for when searching for fragments of O. serratus. Tig. 15 illustrates 

 perfectly the sub-genus SphcBrophthalmus, while it is also a common Upper Lingula 

 riag fossil for Britain (see Mem. Geol. Surv., vol. iii. ined., pi. 4). Fig. 17 is Angelin's 

 sub-genus Leptoplastus, which I regard as a form of SphcBrophthalmus, and may illus- 

 trate in part our O. pec ten and O.Jlagellifer. Olenus proper and Peltura are sufficiently 

 represented by our own species^ 



