778 



ARTHROPODA 



PHYLUM VII 



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

 Sd tekon, all with smooth surfaces. The first five Segments w. h 

 i^" 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). 



Order 3. BURYPTBRIDA Burmeister. ^ 



Body elongated, luith a thin chitinous epi- 

 dermal campace ornamented hy fine scale-like 

 ■markings. Prosoma with two 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 hordered posteriorly hy a metastoma. 

 "Abdomen" consisting of thirteen free segments, 

 of which the anterior six helong to the mesosoma 

 q.nd hear ventrally five pairs of hroad, foliaceous 

 appendages, corresponding or comparahle to the 

 operculum and hranchial appendages of Limulus. 

 The metasoma consists of six free, annular seg- 

 ments without appendages, together with a long 

 or spatulate telson. 



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

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



' Literature : Dekay, J. £., On a Fossil Crustaceous Animal. Ann. N.Y. Lyc. Nat. Hist., 

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

 iv. — Roemer, F., Ueber ein Exemplar von Eurypterus. Palaeontogr. , 1851, vol. i. — Huxley, T. IL, 

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

 gotus. Mem. Geol. Surv. United Kingd., 1859, vol. I—Page, D., Advanced ^ext-Book of Geology, 

 1856 and 1S59. —NieskowsM, J., De Euryptero remipede. Dorpat, 1858. — Hall, J., Palaeon- 

 tology of New York, 1859, vol. iii. — Salier, 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., xxvii., xxviii., etc., 1864-72. 

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

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

 gotus, etc.). Bull. Buffalo Soc Nat. Sei., 1875, vol. in.— Pohlman, J., Fossils of the Water-Lime 

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

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

 Acad. Imp. Sei. St-Petersb., 1883, ser. 7, vol. xxxi.—IIaü, J., Note on Eurypteridae. 2nd Geol. 

 Survey Penn., Rept. PPP., lS8i.— /dem, and Clarke, J. M., Palaeontology of New York State, 

 1888, vol. \\\.—Whiteaves, J. F., Palaeozoic Fossils of Canada, 1884, vol. iii. — Fraipont, J., 

 Eurypterides nouveaux du Devonien. Ann. Soc. Belg. Geol., 1889, vol. xvn.—Claypole, E. W., 

 On Eurysoma, Carcinosoma, etc. Amel-. Geol., 1890-94, vols. vi., xiii. — Laurie, M., Eurypterid 

 Remains from Pentland Hills. Trans. Roy. Soc. Edinb., 1892, vol. xxxvii.— Idem, On Eurypterida. 

 Nat. Sei., 1893, vol. m.—Idem, Anatomy and Relations of the Eurypteridae. Ibid., 1893, vol. 

 xxxvii., and Nat. Sei., 1893, vol. m.—Holm, Q., Über Eurypterus Fischeri. Bull. Acad. Imp. 

 Sei. St-Petersb., 1896, ser. 5, vol. iv. ; also Memoires, 1898, ser. 8, vol. vüi., and Geol. För. i 

 Stockholm För., 1899, vol. xxx.—Semper, M., Gigantostraken des böhmischen Paläozoicum. Beitr. 

 Pal. u. Geol. Osterr.-Ung., 1898, vol. n.—Beecher, C. F., Restoration of Stylonurus. Amer. 

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

 Geol. Mag. 1900, dec. 4, vol. yin.—Sarle, C. /., Eurypterid Fauna from the Salina Rept. N.Y. 



Fio. 1504. 



Pseudoniscus roosevelti Clarke. Complete 

 indivldual. Silurian (Salina Group) ; Monroe 

 County, New York, '^/i (after Clarke). 



