Vol. 52.] FAUNA OF THE KEISLEY LIMESTONE. 427 



describe it as a new one. The base of a parallel-sided cylindrical 

 glabella is seen with a pair of very narrow elongated basal lobes 

 pressed close against its sides. These lobes do not measure in width 

 more than one-third of the width of the glabella. Outside each of 

 these lobes is a broader, rounded, swollen ridge, running forward 

 and curving slightly inward. At the base of the axal furrow which 

 separates this ridge and the basal lobe is a deep pit. The narrow 

 neck-lobe at the base of the glabella is furnished with a very strong 

 central tubercle. 



millim. 



Length 2*5 



Breadth 4:0 



LlCHAD^. 



Lichas laxatus, M'Coy. 



One extremely sharp cast of the pygidium of this well-known 

 species shows all the typical features, which need no description. 



Lichas afflnis, Angelin. 



The occurrence of this characteristic species of the Leptcena- 

 Limestone in the Keisley Limestone is established not only on the 

 evidence of a head-shield, but also on that of several pygidia, of 

 which one, fairly well preserved, is in the Woodwardian Museum. 

 Angelin's l original figures and description were inadequate and 

 unsatisfactory, but by means of Tornquist's 2 more recent diagnosis 

 and illustrations, and by comparison with actual Dalecarlian speci- 

 mens, I have no doubt of the correct identification of the English 

 individuals. 



Measurements. 



milliin. 



Length of median lobe of glabella 15'0 



Width of do. across anterior end 160 



Width of do. at the level of the posterior end of the 



first side-lobes 6'0 



Length of first side-lobe 100 



Width of do. 6-0 



Length of pygidium (so far as preserved) 24*0 



Estimated length of do. when perfect 38 - 



Width of do. along anterior edge 41 



Width of do. at level of axal knob 440 



Width of axis at anterior end 13 



Width of do. at end of axal furrows &5 



Length of do. to end of axal furrows 130 



Greatest width of post-axal area 11 



Lichas cojsfoemis, Ang., var. keisleyknsis, nov. (PI. XXI. fig. 10.) 



For the determination of this species we have again to rely upon 

 a single imperfect specimen of a pygidium and on Angelin's figuro 

 and brief description. 3 Since the Swedish and Keisley forms agree 



1 Angelin, ' PaJseont. Scandin.' 1854, pi. xxxviii. fig. 4, p. 69. 



2 Tornqnist, ' Undersokn. ofv. Siljans. Trilob.' Sver. geol. Undersokn. 1884, 

 pi. i. fig. 31, p. 33. 



3 Angelin, op. supra cit. pi. xxxviii. fig. 5, p. 74. 



