CHEIRURUS BIMUCRONATUS. 139 



1840. Calymeue speciosa, Hisinger, Leth. Suec, 2nd suppl., pi. xxxix, fig. 2. 



1843. Arges bimucronatus, Goldfuss, Neues Jahrb., p. 544. 



1845. Cheirurus bimucronatus, Beyrich, Ueber biihm. Trilob., pp. 18, 19. 



— Cheirurus insignis, Beyrich, ibid., fig. i 1. 



? 1846. Cheirurus insignis, Barrande, Not. prelim., p. 49. 



1848. Cheirurus speciosus, Salter, Mem. Geol. Surv., vol. ii, pt. i, p. 345, pi. vii, figs. 4 — 6. 



1849. Ceraurus williamsii, M'Coy, Ann. Mag. Nat. Hist. [2], vol. iv, p. 408. 

 1851. Cheirurus bimucronatus, Salter, Quart. Journ. G-eol. Soc, vol. vii, p. 172. 



? 1851. Cheirurus speciosus, Angelin, Pal. Scand., p. 78, pi. xxxix, fig. 14; pi. xli, fig. 15. 



? 1852. Cheirurus insignis, Barrand>>, Syst. Silur. Boheme, vol. i, p. 782, pi. xli, figs. 1 — 13. 



1853. Cheirurus bimucronatus, Salter, Mem. Geol. Surv., dec. vii, pi. ii. 



1854. Ceraurus williamsii, M'Coy, Synops. Brit. Pal. Foss. Woodw. Mus., p. 155, pi. i f, fig. 13. 

 — • Cheirurus bimucronatus, Morris, Cat. Brit. Foss., 2nd ed., p. 103. 



1864. Cheirurus bimucronatus, Salter, Mon. Brit. Trilob., p. 63, pi. v, figs. 1—5 ; pi. vi, figs. 9 — 18. 



1866. Cheirurus bimucronatus, Salter, Mem. G-eol. Surv., vol. iii, p. 323, pi. xviii, figs. 4 — 6. 



1867. Cheirurus bimucronatus, Murchison, Siluria, 4th ed., pi. iii, fig. 5; pi. xix, figs. 10, 11. 

 1873. Cheirurus bimucronatus, Salter, Cat. Camb. Silur. Foss. Woodw. Mus., pp. 77, 86, 130. 



1876. Cheirurus bimucronatus, Armstrong and Young, Cat. West. Scot. Foss., p. 15. 



1877. Cheirurus bimucronatus, Woodward, Cat. Brit. Foss. Crust., |>. 30. 



1878. Cheirurus bimucronatus, Nicholson and Etheridire (e. p.), Mon. Silur. Foss. Girvan, fasc. i, 

 p. 100. 



1879. Cheirurus bimucronatus, Nicholson and Etheridge, ibid., fasc. ii, p. 202, pi. xiv, fig. 9. 



1884. Chiriirus speciosus, Toruquist, Siljans. Tiilobitf. (Sver. Geol. Undersokn., ser. C, no. 66), 

 P . 12. 



? 1884. Chirurus insignis, Toruquist, ibid., p. 12, pi. i, fig. 9. 



1885. Chirurus bimucronatus, Lindstrom, Forteckn. Gotl. Silur. Crust., p. 45. 



— Chirurus speciosus, Lindstrom, ibid., p. 44, pi. xii, fig. 11. 



1899. Cheirurus bimucronatus, Mem. Geol. Surv., Silur. Eocks Brit., vol. i, Scotland, pp. 524, 532, 

 538, etc. 



1900. Chirurus bimucronatus, Wiman, Bull. Geol. Instit. Upsala, no. 10, vol. v, pt. ii, p. 169. 



Remarks. — This species occurs in both the Ordovician and Silurian beds of the 

 Girvan district. Nicholson and Etheridge's figured specimen (op. cit., pp. 100, 202, 

 pi. xiv, fig. 9) came from Drunnnuck. Some unusually large specimens come from 

 Thraive Glen, and are in Mrs. Gray's collection; one of these has a glabella 

 measuring at least 42 mm. in length and a thorax over 65 mm. in width. 



A pygidium, probably attributable to this species, from Newlands (Mrs. Gray's 

 collection), is remarkable for the great development of the first pair of pleura?, 

 which reach back as free spines to double the length of the pygidium, while the 

 second and third pairs are only of moderate length, and the members of the latter 

 pair are in contact in the middle line, there being no central terminal point to the 

 pygidium. A similar pygidium has been noticed by me from Woodland Point, but 

 this has a very short central terminal point. There is considerable variation in 

 the relative size of the pleura? of the pygidium and in the length of the spines 

 amongst typical Wenlock examples in England ; but the excessive development of 

 the first pair of pleurae recalls C. exsul, Beyr., and C. gladiator, Eichw. 



