PHACOPS ELEGANS. 155 



1858. Phacops stokesi, Schmidt, Archiv Naturk. Liv.-, Est.-, Kurl., ser. i, vol. ii, p. 184 



1860. Phacops latifrons, Eichwald (e. p.), Leth. ross., p. 1428. 



1864. Phacops stokesi, Salter (e. p.), Mon. Brit, Trilob., p. 21. 



1865. Phacops elegans, Kjerulf, Veiviser, pp. 20, 21, fig. 31 b. 



1873. Phacops stokesi, Salter (e. p.), Cat. Camb. Silur. Foss. Woodw. Mus., p. 76. 



1876. Phacops stokesi, Armstrong and Young, Cat. West. Scot. Foss., p. 16. 



1877. Phacops stokesi, Woodward (e. p.), Cat. Brit. Foss. Crust., p. 56. 



1878. Phacops stokesi, Nicholson and Etheridge, Mon. Silur. Foss. Girvan, fasc. i, p. 98. 



— Phacops hrongniarti, Nicholson and Etheridge (e.p.), ibid., pi. vii, fig. 2 (non fig. 1). 

 1881. Phacops elegans. Marr, Proc. Yorks. Geol. Polyt. Soc, vol. vii, p. 397. 



— Phacops elegans, Schmidt, Rev. Ostbalt. Silur. Trilob., pt, i, p. 72, pi. i, fig. 1 ; pi. x, figs. 

 10-12; pi. xi, fig. 17. 



? 1884. Phacops elliptifrons, Tornquist, Undersokn. Siljans. Trilobitf., p. 8, pi. i, figs. 1 — 3 (Sver. 

 Geol. Undersokn. , Ser. C, no. 66). 



1887. Phacops elegans, Marr, Geol. Mag. [3], vol. iv, p. 35. 



1888. Phacops stokesi, Wigand, Zeitschr. deutsch. Geol. Gesell., vol. xl, p. 40, pi. vi, fig. 1. 



1888. Phacops elegans, Marr and Nicholson, Quart. Journ. Geol. Soc, vol. xliv, -p. 720, pi. xvi, 



figs. 1—4. 

 1899. Phacops stokesi, Mem. Geol. Surv., Silur. Rocks Brit, vol. i, Scotland, pp. 529, 532, 536, etc. 



[{'■mark*. — The specimens from Girvan which are usually attributed to 

 P. stokesi, M. Edwards, are referable, so far as I have seen, to the closely allied 

 species P. elegans. Wigand and others have, indeed, considered the latter specifi- 

 cally inseparable from P. stokesi ; but Schmidt has pointed out the manner in which 

 it differs, and Marr and Nicholson {Joe. eit.) have figured British specimens from 

 the Stockdale Shales. In P. stokesi the glabella expands more rapidly towards the 

 front, and the eyes are relatively larger. The glabellar furrows appear to be 

 similar in the two species, and there is no obvious difference in the thorax and 

 pygidium. The Girvan examples have 7- — 8 segments on the axis of the 

 pygidium, and four pairs of pleurae on the lateral lobes, but the fourth pair is 

 generally very faint; the pleuras are furrowed towards their extremities. The axis 

 is usually about three quarters the length of the pygidium. In a specimen from 

 Newlands in Mrs. Gray's collection which perhaps is referable to this species, 

 there are five pairs of pleurae on the lateral lobes of the pygidium. 



The species belongs to the subgeneric group Phacopidella, which partly 

 corresponds with the imperfectly defined subgenus for which the pre- occupied 

 name Acaste is generally employed. 1 



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

 Museum ; Woodwardian [Sedgwick] Museum. 



Horizons and Localities. — Mulloch Hill Group (L. Llandovery) : Mulloch Hill; 

 Craigens. Saugh Hill Group (M. Llandovery) : Newlands ; Woodland Point. 

 Camregan Group (U. Llandovery): Bargany Pond Burn; Penwhapple Glen. 

 Penkill Group (Tarannon) : Penkill. 



1 Reed, 'Geol. Mag.' [5], vol. ii, 1905, p. 225. 



