138 TRILOBITES OF GIRVAN. 



from Tyrone, while figs. 8, 10, and 11 illustrate Welsh specimens. There is 

 some doubt in my mind whether the specimens shown in figs. 6 and 7 belong 

 to one and the same species ; for the frontal border of the head-shield is rounded 

 in one (fig. G) and flattened in the other (fig. 7), while the relative sizes of the 

 glabellar lobes also differ. The Welsh specimens, however, agree in the flattened 

 or concave upturned frontal border, in the basal width of the glabella being greater 

 than or equal to the length, in the large size and lateral projection of the basal 

 lobes, in the relatively small size of the second lateral lobes, in the contraction of 

 the glabella immediately in front of the basal lobes, in the comparatively short 

 frontal lobe, in the bifurcation of the posterior pair of lateral furrows, in the axial 

 furrows being sigmoidal in course (though only slightly so), in the eyes being a 

 little in front of the second lateral lobes, in the triangular, rather than transversely 

 quadrate, form of the pygidium, and in the granulose surface (according to Salter). 



Since the name senaria is not available for this form, that of planimarginata 

 is here suggested. 



Collection. — Mrs. Gray ; Museum of Practical Geology. 



Horizon and Locality. — Whitehouse Group (M. Bala) : Shalloch Mill. 



4, 5. Calymene, sp. ind. (a) and (b). 



Remarks. — Two minute and imperfect head-shields of species of Calymene are in 

 Mrs. Gray's collection from the Balclatchie Conglomerate. Neither is sufficiently 

 well preserved to determine or describe the species; but they appear to belong 

 to different species, one (sp. ind. a) with a long narrow glabella reaching the 

 narrow, convex, rounded border, and the other (sp. ind. b) with a broader, 

 shorter glabella having a rather swollen, broad, frontal lobe strongly elevated 

 above the narrow, feebly-rounded border. The head-shield of sp. a measures 

 3 mm. in length and that of sp. b 5 mm. in length. 



Collection. — Mrs. Gray. 



Horizon and Locality. — Balclatchie Group (Llandeilo) : Balclatchie Con- 

 glomerate. 



Family Cheirurid^:. 

 Genus CHEIRURTJS, Beyrich. 

 1. Cheirurus bimucronatus (Murchison), 1839. Plate XIX, fig. 15. 



1839. Paradoxides bimucronatus, Murchison, Silur. Syst., p. 658, pi. xiv, figs. 8, 9. 



1840. Paradoxides bimucronatus, Milne Edwards, Crust., vol. iii, p. 343. 



