BRITISH FOSSILS. 



Decade XI. Plate III. 



ASAPHUS GIGAS. 



[Genus ASAPHUS. Brongniart. (Sub-kingdom Articulata. Class Crustacea. 

 Order Trilobita. Family Asaphidse.) Eyes large, smooth. Facial suture marginal or 

 supramarginal in front, and ending on the posterior margin. No rostral shield. Labrum 

 strongly bifurcate. Body rings eight.] 



[Sub-genus Isotelus. De Kay. Facial suture intramarginal in front, and with 

 a vertical suture beneath ; head scarcely at all lobed ; pleurae much bent down ; tail 

 large, with faint axal furrows and no lateral ribs.] 



Diagnosis. /. ovali-oblongus Icevis, lateribus rectis ; capite pygidioque 

 (Bqualibus subtrigonis hyperbolicis. Caput sulcis axalibus minime pro- 

 fundis. Oculi modici pone medium capitis positi. Sutura facialis 

 intra marginem frontalem parallela ; labro * ad basin angusto, furcis 

 longis parallelis. Thoracis axi pleuris cequali, fulcra ad tertium posito. 

 Cauda axi indistincto angusto conico longo, limbo sulco unico superiore, 

 reliquis ?iullis. 



Synonyms. Asaphus platyceph.^ Stokes (1822), Trans. Geol. Soc, 

 London, i. 8, p. 208, pi. 27. Isotelus gig as and /. planus^ De Kay (1824), 

 Annals of the Lyc. of Nat. Hist, of New York, vol. i. p. 176, pi. 12, 13, 

 fig. 1. Asaphus gigas, Dalm. (1826), Palsead. 71. Isot. gigas, Green 

 (1832), Mon. of Tril., p. 67 ; also /. planus, p. 68, /. sfegops, p. 71, /. 

 Cyclops, p. 69, and /. megalops, p. 70. Brongniartia isotela, Eaton 

 (1832), Geol. Text Book, pi. 2, fig. 19. Asaph, platyceph. Bronn. (1835), 

 Leth., vol. i. p. 115, pi. 9, fig. 8. Asaph, gigas, Emme. (1839), Dissert. 32, 

 12. Isotelus gigas, Milne-Edv7. (1840), Crust., vol. iii. p. 298. Asaph, 

 platyceph., Buckland (1840), Bridg. Treat., vol. ii. p. 76. Asaph, platy- 

 ceph., BuRM. (1843), Org. Tril., pi. 2, fig. 12, Ray, ed. (1846), p. 110. 

 EoRTL. (1843), Geol. Rep. Isot. gigas, pi. 7, figs. 1-4, pi. 8, fig. 7 ; /. planus, 

 pi. 7, figs. 2, 3 (except pi. 8, figs. 2, 3); I, ovatus, pi. 8, fig. 5 ; I, sclerops, 

 pi. 10, fig. 2 ; /. Powisii, pi. 6, fig. 1. /. megistos, Locke (1842), Araer. 

 Journ. Science, vol. xlii. p. 366 ; Trans. Assoc. American Nat. and Geolo- 

 gists (1843), vol. i. pi. 6. /. gigas. Hall (1847), Pal. New York, pi. 60, 

 fig. 7 ; pi. 61, figs. 3, 4 ; pi. 62, figs. 1, 2; pi. 63. /. gigas, Billings (1863), 

 Geol. of Canada, p. 184, fig. 182 (and /. platycephalus, ib. fig. 183?) 



* I prefer this term to hypostome, used in the former Decades. The hypostome of 

 Dalman is the incurved front margin. 



[xi. iii.] 11 c 



