96 TRILOBITES OF GIRVAN. 



A single but well preserved head-shield of tins well-known species, which has 

 not been hitherto recorded from the Girvan district, occurs on a slab of rock con- 

 taining EiicrtiiHfiis punctatus from the Wenlock Series of Knockgardner, Straiten. 



Colled tun. — Edinburgh Museum. 



Horizon and Locality. — Wenlock Series : Knockgardner ; Straiten. 



2. Lichas (Corydocephalus) geikiei, Nicholson and Etheridge, 1879. Plate XII 1, 

 figs. U, 14 a; plate XIV, fig. 1. 



1879. Lichas geikiei, Nicholson and Etheridge. Mori. Silur. Foss. Girvan, fasc. ii, p. 137, pi. x, fig. 1. 

 1899. Lichas geikiei, Mem. Geol. Surv., Silur. Rocks Brit., vol. i, Scotland, pp. 524, 673, 689. 

 1902. Lichas geikiei, Reed, Quart. Journ. Geol. Soc, vol. lviii, p. 76. 



Specific Characters. — Head-shield strongly convex and much bent down at the 

 sides, but less so in front; semicircular in shape. The glabella is tumid, and the 

 median lobe is swollen and projects considerably in front of the bicomposite lobes, 

 expanding regularly in width anteriorly from their base and slightly embracing 

 them in front. The bicomposite lobes are short, being not more than half the 

 length of the glabella ; their reniform shape is distinct and there is a narrow trans- 

 verse furrow across them starting from the internal notch in the course of the first 

 lateral furrows ; their posterior outer lateral angles are feebly marked out by nearly 

 obsolete furrows. The first lateral furrows converge posteriorly at about 30° and 

 bend outwards sharply at the base of the bicomposite lobes to end suddenly in 

 deep pits ; a shallow groove runs backward from each pit to the inner angle of the 

 occipital lobe. The fourth lateral lobe J is imperfectly defined on its outer, anterior, 

 and posterior sides owing to the weakness or disappearance of the furrows. The 

 occipital lobes are sub-triangular rather than oval, and are incompletely defined at 

 the anterior outer angle. The fourth lateral furrows defining them thus incom- 

 pletely in front are situated at the level of the middle portion of the neck-ring, and 

 appear to arise in a line with the neck-furrow. The axial furrows vary in strength 

 along their course, being well marked as far back as near the posterior end of the 

 bicomposite lobes (where they diverge outwards), but become practically obsolete 

 outside the indistinct fourth lateral lobes; they then again increase in strength 

 and run back to the base of the occipital lobes curving strongly inwards. The 

 median portion of the glabella behind the base of the bicomposite lobes is slightly 

 swollen as a post-median lobe and bears a large median tubercle. The fixed cheeks 

 are strongly convex and slope down steeply at the sides and in front. The eye is 

 of moderate size, prominent, and placed opposite the middle of the bicomposite 

 lobes, not far from the axial furrows. The free cheeks are triangular with an 



1 Reed, 'Quart. Journ. Geol. Soc.,' vol. lviii (1902), p. 64. 



