14 TRILOBITES OF GIRVAN. 



Collections. — Mrs. Gray ; Museum of Practical Geology, Jermyu Street ; Edin- 

 burgh Museum; Woodwardian Museum. 



Horizon and Locality. — Balclatcliie Group (Llandeilo) : Dow Hill ; Balclatchie 

 Conglomerate. 



4. Trinucleus, sp. ind. (a). Plate II, figs. 7, 7 a, 7 b. 



1879. Trinucleus, sp. ind. a., Nicholson and Etheridge, Mon. Silur. Foss. Girvan, fasc. ii, p. 198, 

 pi. xiv, fig. 2. 



Specific Characters. — Head-shield semicircular; fringe flattened, slightly bent 

 down, widest at genal angle. Genal angle provided with strong spine of moderate 

 length, projecting outwards, slightly curved backwards and longitudinally grooved 

 on upper surface. Fringe possesses two outer regular rows of radially arranged 

 pits, becoming confluent near genal angles. Inside these two rows are 2 — 4 

 regular rows of more or less radially arranged pits of equal size in front of the 

 cheeks and glabella, but becoming irregular in arrangement and more numerous 

 near genal angles. Fringe increases in width towards genal angles, but is scarcely 

 at all produced backwards. A narrow raised angular border surrounds it. 

 Glabella possesses ovoid swollen frontal lobe, not overhanging fringe ; posterior 

 portion unknown. Cheeks triangular, gently convex, sloping gradually down 

 to fringe. Ocular tubercle present. Surface of glabella and cheeks coarsely 

 reticulate. 



Remarks. — The fragment of the genal angle and fringe of a species of 

 Trinucleus described by Nicholson and Etheridge as ' sp. ind. o ' corresponds with 

 the fringe attached to several fragmentary head-shields from the same locality in 

 Mrs. Gray's collection. The above somewhat fuller description of the form is 

 therefore now possible, though not sufficient for its specific determination. 



Affinities. — This form is scarcely sufficiently preserved to determine its affinities, 

 but it seems more to resemble T. concentricus than T. buchlandi. 



Collections. — Mrs. Gray (f. M.) ; Museum of Practical Geology ; Edinburgh 

 Museum ; Woodwardian Museum. 



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



5. Trinucleus, sp. ind. (/;). Plate II, figs. 8, 8 a. 



1879. Trinucleus, sp. ind. b, Nicholson and Etheridge, Mon. Silur. Foss. G-irvan, fasc. ii, p. 198, 

 pi. xiv, fig. 3. 



Llemarlcs. — The specimen which Nicholson and Etheridge figured consists of 

 only one cheek and a portion of the fringe. There are, however, some better 

 specimens of the whole head-shield in Mrs. Gray's eollection. It is probable that 



