L60 TEILOBITES OF G1RVAJ*. 



On the whole the Girvan specimens appear to be specifically distinct from any 

 hitherto described, and the name /'. bisseti may be appropriately given to them. 



Collections. — Mr. Bisset (Edinburgh) ; Mrs. Gray. 



Horizon and Locality. — Drummuck Group (U. Bala): Lady Burn; Thraive 

 Glen (Starfish Bed). 



SUPPLEMENTARY NOTES. 



Family Tiunucleid.k. 

 Genus TRINUCLEUS, Llwyd. 

 Trinucleus, sp. ind. (6). 



1903. Trinucleus, sp. ind. (b), Reed, supra, p. 14, pi. ii, figs. 8, 8 a. 



Within a space measuring 40 X 50 mm. on one slab of rock from Whitehouse 

 Bay, there are three well-preserved head-shields of the trilobite described as 

 Trinucleus sp. ind. (b). The fringe is poorly exposed and shows only one concentric 

 row of large pits in front, probably due to the radial fusion of the pits of the two 

 rows previously described, since 2 — 3 rows are present at the genal angles. In the 

 former description it was stated that the surface of the glabella is smooth, but this 

 is not the case with these new specimens, which have the shell perfectly preserved, 

 for a fine reticulation, which gives the appearance of a honeycombed, pitted surface, 

 ornaments the swollen ovoid portion of the glabella. An isolated small, round, 

 submedian tubercle is also present on this part. The neck of the glabella and the 

 cheeks are, however, quite smooth and devoid of any reticulation or tubercles ; no 

 ocular tubercles can be detected. The peculiar lobeless, subcylindrical neck is 

 somewhat contracted at its base, and is only about one fourth the length of the 

 whole glabella. The glabella does not overhang the fringe at all in front, but ends 

 well inside it, sloping down to it rather more gradually than to the neck, the apex 

 of the ovoid lobe being post-median. The dimensions of the three head-shields 

 are as follows : 



I. II. III. 



Length . 10*5 . 1.1*5 . 775 mm. 



Width . 19-5 . 20-0 . 12-00 „ 



( Collection. Mrs. Gray. 



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



