102 TRILOBITES OF GIRVAN. 



6. Lichas (Platylichas) laxatus, M'Coy, 1846. Plate XIV, figs. 11—13. 



1846. Lichas laxata, M'Coy, Synops. Silur. Foss. Ireland, p. 51, pi. iv, fig. 9. 



? — Lichas pumila, M'Coy, ibid., p. 52, pi. iv, fig. 8. 



— Calymene? forcipata, M'Coy (e.p.), ibid., p. 48, pi. iv, fig. 14 (tail). 



1848. Lichas laxatus, Salter, Mem. Geol. Surv., vol. ii, pt. i, p. 340, pi. viii, figs. 4, 5, 6. 



1851. Lichas laxatus, Salter, Quart. Journ. Geol. Soc, vol. vii, p. 172, pi. ix, fig. 5. 



1854. Lichas laxatus, Morris, Cat. Brit. Foss., 2nd ed., p. 110. 



? — Lichas sexspinus, Angelin, Pal. Scand., p. 74, pi. xxxviii, figs. 7, 8. 



? — Lichas aculeatus, Angelin, ibid., p. 75, pi. xxxviii, fig. 11. 



1866. Lichas laxatus, Salter, Mem. Geol. Surv., vol. iii, p. 324, pi. xix, figs. 1 — 3. 

 Lichas segmentatus, Linnarsson, Silur. bildn. i. mell. Vesterg., p. 18, pi. xi, fig. 4 



1867. Lichas laxatus, Murchison, Siluria, 4th ed., p. 204, foss. 46, fig. 5. 

 1869. Lichas laxatus, Linnarsson, Vestergotl. Camb. Silur. Aflagr., p. 66. 

 1873. Lichas laxatus, Salter, Cat. Camb. Silur. Foss. Woodw. Mus., p. 50. 

 1875. Lichas laxatus, Baily, Figs. Char. Brit. Foss., p. 40, pi. xiii, figs. 7a, h. 



1877. Lichas laxatus, Woodward, Cat. Brit. Foss. Crust., p. 43. 



1878. Lichas laxatus, Nicholson and Etheridge, Mon. Silur. Foss. Girvan, fasc. i, p. 131. 



— Lichas, sp. ind., Nicholson and Etheridge, ibid., p. 135, pi. ix, figs. 13, 14. 



1884. Lichas laxatus, Toruquist, Siljansom. Trilobitf. (Sver. Geol. Undersokn., Ser. C, No. 66), p. 31. 



1885. Lichas laxatus, Schmidt, Kev. Ostbalt. Silur. Trilob., pt. ii, p. 125. 

 1896. Lichas laxatus, Keed, Quart. Journ. Geol. Soc, vol. Hi, p. 427. 

 1902. Lichas laxatus, Eeed, Quart. Journ. Geol. Soc, vol. lviii, pp. 76, 82. 



Remarks. — There is an interesting, though imperfect, specimen of this common 

 but imperfectly known species in Mrs. Gray's collection from Thraive Glen, 

 showing a portion of a head-shield, with the free cheek bearing the eye in a 

 remarkably good state of preservation, and ten segments of the thorax attached. 

 The minute structure of the eye of this species does not appear to have been pre- 

 viously described. In this example the large semicircular prominent eye-lobe is 

 bent slightly upwards, has a broad swollen margin, and is marked off from the 

 small fixed cheek by a wide but shallow groove. The eye itself is lunate, very 

 large, with a high vertical lens-bearing surface, like PJtacops, slightly higher at 

 the anterior than the posterior end, and with a narrow furrow round its base. The 

 lenses are hexagonal, very minute, closely packed and arranged in numerous 

 vertical rows. Across the middle of the eye there are 40 — 50 lenses in one vertical 

 row. So far as the characters can be made out, the eye has the structure of the 

 Asaphids, and belongs to Lindstrom's Group I in his classification of trilobites 

 according to the structure of the eyes. 1 



In the thorax the axis is cylindrical, gently convex, and hardly tapering at all 

 posteriorly. Each axial ring has a rounded articulating band, arched forwards, on 



1 Lindstrom, ' Kongl. Svensk. Vet. Akad. Handl.,' vol. xxxiv, No. 8 (1901), pp. 26, 27. 



