778 



ARTHEOPODA 



PHYLUM VII 



gradually tapering median axis. Segments nine in number, besides a short 

 pointed telson, all with smooth surfaces. The first five segments with 



obliquely grooved pleura ; sixth and seventh 

 partly conjoined on the pleura, and corre- 

 sponding axial parts of the segments narrow ; 

 eighth and ninth segments narrow, lanceolate, 

 and with increasing retral curvature. Average 

 total length of animal 2 "5 cm. Silurian; 

 Oesel and New York State (Salina Group). 



j Orders. EURYPTBRIDA Burmeister.^ 



Body elongated, with a thin cldtinous epi- 

 dermal carapace ornamented by fine scale -like 

 markings. Frosoma with tiuo large, sometimes 

 facetted lateral eyes and a pair of median ocelli ; 

 on the ventral side with six pairs of appendages, 

 the foremost of which is preoral and chelicerate. 

 Mouth bordered posteriorly by a metastoma. 

 " Abdomen " consisting of thirteen free segments, 

 of which the anterior six belong to the mesosoma 

 and bear ventrally five pairs of broad, foliaceous 

 appendages, corresponding or comparable to the 



operadum and branchial appendages of Limulus. 

 Fio. 1504. jL . ^-'^-^ - ^ -^ , 



PseudoniscuB rooseveiti Clarke. Complete ^^'^ mctasoma cmsists of SIX free, annular seg- 



individual. Silurian (Salina Group); Monroe ments without appendages, together with a loug 

 County, New York. »/i (after Clarke). , , , _, 7 i> ' J 



or spatutate telson. 



This order, which is restricted wholly to the Paleozoic, embraces the largest 

 Arthroijods known, some of them {Pterygotus, Stylonurus) having attained a length 



1 Literature: Dekay, J. E., On a Fossil Crustaceous Auimal. Ann. N.Y. Lye. Nat. Hist., 

 1825, vol. i.—M'Coij, F., Some British Fossil Crustacea. Ann. Mag. Nat. Hist., 1849, ser. 2, vol. 

 iv. — Roemer, F., Ueber ein E.xemplar von Eurypterus. Palaeontogr. , 1851, vol. i. — Huxley, T. //., 

 On Himantopterus. Quar. Journ. Geol. Soc, 1856, vol. xii. — Idem, and Salter, J. W., On Ptery- 

 gotus. Mem. Geol. Surv. United Kingd., 1859, vol. i.—Page, D., Advanced Text-Book of Geology, 

 1856 and ISb'd.—Nieskowski, J., De Euryptero remipede. Dorpat, 1858.— ^a^/, J., Palaeon- 

 tology of New York, 1859, vol. m.— Salter, J. W., Some Fossil Crustacea, etc. Quar. Journ. Geol. 

 Soc, 1862-63, vols, xviii., xix. — Woodward, H., Numerous papers in Geol. Mag., ser. 1, dec. 1, 

 vols, i., ix., and Quar. Journ. Geol. Soc, vols, xxi., xxiii., xxiv., x.xvii., xxviii., etc, 1864-72. 

 — Idem, Monograph of British Fossil Crustacea, Order Merostoniata. Palaeontogr. Soc, 1866-78. 

 —Grate, A. R., and Pitt, W. H., New Crustaceans from Water- Lime Group (Eusarcus, Ptery- 

 gotus, etc.). Bull. Burtalo Soc Nat. Sci., 1875, vol. m.^Pohlman, J., Fossils of the Water-Lime 

 Group. Ibid., 1881-84, vols, iv., v. — Peach, B. N., Further Researclies among Crustacea and 

 Arachnida. Trans. Roy. Soc. Edinb., 1882, vol. xxx.— Schmidt, F., Miscellanea Silurica. Mem. 

 Acad. Imp. Sci. St-Petersb., 1883, ser. 7, vol. xxxl—Hall, J., Note on Eurypteridae. 2nd Geol. 

 Survey Penn., Rept. PPP., 188^.— Idem, and Clarke, J. M., Palaeontology of New York State, 

 1888, vol. \\\.— Whiteave.s, J. F., Palaeozoic Fossils of Canada, 1884, vol. in.— Fraipont, J., 

 Euryptc'Tides nouveaux du Devonien. Ann. Soc. Belg. Geol., 1889, vol. x\\\.—Clctypole, E. W., 

 On Eurysoma, Careinosoma, etc Amer. Geol., 1890-94, vols, vi., xm.— Laurie, M., Eurypterid 

 Remains from Pentland Hills. Trans. Roy. Soc Edinb., 1892, vol. xxx\\\.—Idevi, On Eurypterida. 

 Nat. Sci., 1893, vol. \\\.—Idem, Anatomy and Relations of the Eurypteridae. Ibid., 1893, vol. 

 xxxvii., and Nat. Sci., 1893, vol. m.—Holvi, G., tjber Eurypterus Fischeri. Bull. Acad. Imp. 

 Sci. St-Petersb., 1896, ser. 5, vol. iv. ; also Memoires, 1898, ser. 8, vol. viii., and Geol. For. i 

 Stockholm Fiir., 1899, vol. x\\.— Semper, M., Gigantostraken des bohmischen Palaozoicum. Beitr. 

 Pal. u. Geol. Osterr.-Ung., 1898, vol. \\.—Beccher, C. E., Restoration of Stylonurus. Amer. 

 Journ. Sci., 1900, vol. x.—Idem, Eurypterid Remains from Missouri. Ibid., 1900, vol. xii., and 

 Geol. Mag. 1900, dec. 4, vol. viii. —^'ar^e, C. /., Eurypterid Fauna from the Salina Rept. N.Y. 



