Vol. 65.] ROCKS OF THE TOTJEMAKEADY DISTRICT. 145 



are followed by a short triangular piece wedged in between the 

 bases of the last pair of pleurae and forming the tip of the axis. 

 The axial furrows are weak. The pleurae of the lateral lobes 

 are unfurrowed, have a flattened, elongated, and sublobate shape, 

 and obtusely rounded ends which are free. The first and second 

 pleurae are in contact for nearly three-fourths of their length, 

 and widen a little towards their extremities, diverging from the 

 axial line. The second and third pleurae are likewise in contact, 

 but only for a little more than half their length. The third pair of 

 pleurae are nearly parallel-sided, and run back in contact in the 

 middle line for nearly half their length with only a very slight 

 divergence. The three pairs of pleurae arise from the last three 

 rings of the axis, and the last pair therefore does not correspond 

 with the triangular segment at the tip of the axis, which thus seems 

 to be devoid of pleurae or to be of the nature of a post-axial piece. 



The general characters of this pygidium suggest a comparison 

 with PI. actinura (Dalm.) rather than with PL pseudo-articidata ; 

 but it has the divergent pleurae and broadly conical axis of the 

 first with the obtusely-ended pleurae of the second. The absence of 

 the fusion of the members of the last pair of pleurae which is so 

 marked in PL pseudo-articulata is a striking difference, and the 

 blunt extremities of the pleurae are in contrast with the pointed 

 extremities of those in PL actinura? 



In Pl.fisclieri (Eichw.)'" Ave find the axis of the pygidium of not 

 quite so sharply conical a shape, but the terminal triangular 

 segment bears no pleurae. The blunt extremities of the pleura? 

 also agree with this Mayo specimen, and the manner in which the 

 last pair of pleurae lie in median contact behind the axis. All the 

 pleurae, however, lie subparallel, diverging less in a fan-shaped way ; 

 they are also, relatively, not so broad. But it is undoubtedly the 

 case that Pl.fisclieri and this Irish species are closely allied. 



Dimensions : — 



Length of fragmentary pygidium 9 millimetres. 



Width of fragmentary pygidium 17 ,, 



Length of axis 4*5 „ 



Length of 3rd pleura; 5 - 5 ,, 



Pliomera aff. barrandei, Billings. (PI. VI, fig. 5.) 



There is one imperfect pygidium in the rotten crumbling rock 

 from the spot (293), 1 mile west of Drumcoggy Rectory, which 

 bears a great resemblance to Billings's Amphion [ — Pliomera~] 

 barrandei from the Quebec Group. 3 The axis is perfect, as also 

 the left lateral lobe and pleural spines, though their preservation 

 as external impressions renders the characters somewhat difficult 



1 C. Wiman, ' Studien iiber das Nordbaltische Silurgebiet, II ' Bull. Geol. 

 Inst. Univ. Upsala, vol. viii (1907) p. 87 & pi. vii, figs. 9-12. 



2 F. Schmidt, 'Kev. Ostbalt. Silur. Trilob.' pt. i, Mem. Acad. Sci. St. Petersb. 

 ser. 7, vol. xxx, no. 1 (1881) p. 191 & pi. xiii, figs. 1-8. 



3 E. Billings, 'Palieoz. Fuss. Canada' vol. i (1865) p. 288 & fig. 277 6. 

 Q. J. G. S. No. 258. i 



