16 TBJLOBITES OF GIRVAN. 



sharply marked off from cheeks, composed of 3 — 4 concentric rows of small pits 

 in front and 4 — 5 laterally. Genal angles not produced backward but armed with 

 very short broad spines. 



Pygidium broadly subtriangular with wide bevelled striated border ; conical 

 axis about one fourth the width of pygidium, possessing 5 — 7 rings with a pair of 

 pits in the furrows between them. Lateral lobes flat with 2 — 3 indistinct pleurae. 



Dimensions. — 



Length. Width. 



(1) Head 4 - 5 mm. CrO mm. 



(2) Pygidium 3 - mm. 8*0 mm. 



Remarks. — Some small head-shields and pygidia from the Bala beds of White- 

 honse Bay in Mrs. Gray's collection, apparently belonging to the same species, 

 possess the above characters, and seem to mark a distinct species, but the 

 material is too imperfect and scanty for a more detailed diagnosis. 



Collection .■ — Mrs. Gray. 



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



8. Trinucleus, sp. ind. (e). 



1880. Trinucleus, sp. ind., Nicholson and Etlieridge, Mon. Silur. Foss. Grirvan, fasc. iii, p. 288, 

 pi. xix, fig. 10. 



Remarks. — The crushed specimen of a head-shield, figured by Nicholson and 

 Etlieridge as ' Trinucleus, sp. ind.,' is in a very poor state of preservation, but the 

 broad fringe with its backwardly produced genal angle appears to have some of 

 the characters of Tr. buckldndi. The surface of the glabella and cheeks is 

 reticulate, but not so coarsely as in Trinucleus, sp. ind. d, and there is a median 

 tubercle on the glabella not mentioned by Nicholson and Etlieridge. It is 

 impossible to define this form more precisely on account of its very imperfect con- 

 dition, and I much doubt if it is really a distinct species. 



Collection.— Mrs. Gray (f. M.) 



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



9. Trinucleus, sp. ind. (/). Plate II, fig. 11. 



Specific Characters. — Pygidium broad, short, rounded, not triangular, about 

 three times as wide as long. Axis broad, rounded, slowly tapering, occupying 

 nearly the middle third of pygidium ; composed of 5 — G rings of which the first 

 3 — 1< are complete. Lateral lobes flat with 2 — 3 obscure pleurae. 



I 'intrusion*. 



Length ...'■> mm. 



Width . . . 9 „ 



