170 BRITISH PALEOZOIC PHYLLOCARIDA. 



10. Dtthyrocaris tricornis, Scouler, 1835. Plate XXII, fig. 4 (magnified part), 



figs. 5 a — e ; Plate XXIV, figs. 1, 5 a, b, and 6 ; 

 Plate XXV, figs. 9 a, b, c (?) ; Plate XXVII, 

 figs. 2 a, b, c, 4 a — e. 



AitiiAS tricornis, Scouler, 1 1835. Records of General Science (Thomson's), vol. i, 



p. 137, fig. 2; and p. 141. 

 — — Bronn, 1848. Index Palaeont., vol. i, p. 102. 



Dithykocahis trtcornis, Bronn, 1848. Ibid., vol. i, p. 433. 



— — Jlorris, 1854. Catal. Brit. Foss., edit. 2, p. 107. 



— — Salter and Woodward, 1865. Chart Foss. Crust., p. 17, 



fig. 12. 



— — J. Armstrong, 1871. Trans. Geol. Soc. Glasgow, vol. 



iii, Appendix, p. 30; and Catal. W.- 

 Scotl. Fossils, 1876, p. 45. 



— — H. Woodward and It. Etheridge, jun., 1873. Mem. 



Geol. Surv. Scotl., Expl. Sheet 23, 

 Appendix, p. 99; Geol. Mag., vol. x, 

 pp. 483, 480, pi. xvi, figs. 2 and 3. 

 — H. Woodioard, 1877. Catal. Brit. Foss. Crust., p. 73. 

 Bigsly, 1878. Thesaur. Dev.-Carb., p. 249. 



— — R. Etheridge, Jan., 1879. Quart. Journ. Geol. Soc. 



vol. xxxv, p. 466. 



— — J. Coutts, 1884. Trans. Geol. Soc. Glasgow, vol. vii, 



pp. 200 and 327. 



— — E., W., and J., 1887. Rep. Brit. Assoc, for 1S86, 



p. 63. 



— — Etheridge, 1888. Foss. Brit., vol. i, Pakeoz., p. 238. 



— — J. Neilson, 1894. Trans. Geol. Soc. Glasgow, vol. x, 



pt. 1, p. 71. 



Specific Characters. — Subquadrate carapace, occurring in both an expanded 

 (PI. XXIV, figs. 1 and 5) and a folded state (PI. XXIV, fig. 6) ; strongly ridged, 

 both dorsally and laterally and in the cephalic region ; weak juxtadorsal ridges 

 are also present ; the two ventral margius and the dorsal line all end with a 

 strong triangular spine ; and these three, coming into a line at the hinder end of 

 the folded specimen, PI. XXIV, fig. 6, originated the name " tricomis." Surface 

 covered with a delicate reticulation, with thin irregular meshes, which thicken at 

 frequent intervals into small, short, blunt spines. 



1 According to Portlock (' Beport Geol. Londonderry,' 1843, p. 313), Dr. Scouler described this 

 and another species (A. testudineus ?) at the meeting of the British Association at Glasgow in 1840. 

 -Not mentioned in the Report for that year. 



