PHACOPS. 49 



Ph. (Odontochile) caudatus, Brilnnich. PI. Ill, figs. 4 — 18, and PI. IV, figs 1—5, 



including varieties. 



Trilobus caudatus, Brilnnich. Kjobenh. Sellsk. Skrifter, Nye Samml., vol. i, p. 392, 

 1781. 



— — Schlotheim. Nachtriige, 35, 11, 1823. 



Asaphus Brongniart. Crust. Foss., t. ii, fig. 4 (not iii, fig. 9), 1822. 



— — Dalman. Palseadae, t. ii, fig. 4, 1826. 



— — Green. Monogr. Tril. N. Amer., cast 17, 1832. 



— — Bucklcmd. Bridgw. Treat., pi. xlv, figs. 9 — 11,1836. 



— — Murchison. Sil. System, pi. vii, fig. 8 a ; and A. tuberculato- 



caudatus, ibid., fig. 8 6, 1837. 



— — Milne-Edwards. Crust., vol. iii, p. 308 ; and A. tuberculato- 



caudatus, 1840. 



— myops, Konig. Icones Sectiles Foss., fig. 53, 1825 (our PI. Ill, fig. 13, is 



from the original specimen in the British Museum). 

 Phacops caudatus, Emmerich. Dissert., 1839. 



— — Goldfuss. Neues Jahrb., 1843. 



— — Burmeister. Org. Tril., 2nd edit., t. iv, fig. 9, 1846. 



— — Salter. Decade ii, Geol. Surv., 1849 (exclude syu. P. lon- 



gicaudatus), pi. i, figs. 1 — 12, and fig. 15. 

 Dalmania caudata, Emmerich. Neues Jahrbuch, 1845. 



— — Salter. Memoirs Geol. Surv., vol. ii, pt. 1, 1848. 

 Odontochile caudata, M'Coy. Synopsis Pal. Foss. Woodw. Mus., p. 160, 1851 ; 



PI. Ill, figs. 4—17. 

 Var. a, vulgaris. Most of the above synonyms, PI. Ill, figs. 4 — 17. 

 Var. j3, tuberculato-caudatus, Murchison. PI. IV, fig. 1. 

 Var. y, nexilis, Salter. PI. IV. figs. 3 — 5. 

 Var. S, aculeatus, Salter. PI. Ill, fig. 18. 



P. {Odontochile) magnus, 3 — 4-pollicaris ; ovatus, sub-convexus, capite angusto, fronte 

 plus minusve angulato. Oculi magni, pyramidati. Pleura sulcata (fulcro ad dimidium 

 posito) postica recurves. Cauda apice brevi-mucronato, axi 11 — 12-annulato ; costis 

 lateralibus 7, rarius 6, arcuatis, duplicatis, ad marginem leevem abrupte terminalis, 

 recurvis. 



Pour of the varieties are here figured, and I have no doubt there are others. Those 

 selected illustrate the very close connection that exists between this fossil and the so- 

 called species P. longicaudatus. 



In the Decade of the Survey above quoted I ventured to unite these two species, and 

 have still little doubt that the series of figures here given will convince naturalists that all 

 are derived from one stock. But it will not be so easy to convince paleontologists ; and 

 7 



