SUB-CLASS I 



MKKnsToMATA 



segments having a broad axis anl laim-llar plt-iira.- with <liagonal pleural line- 

 posterior portion (" alxlomen ") of l<>ur nan nu, besides 

 a long and acuminate telson. Silurian ; OeseL 



Hemiaspis, Woodw. (/.//////./..>, SalU-r), (Fig. 1416). 

 General form similar to B anodes. Cephalothorax one-half as 

 long as broad, with several grnal spines; r.-ntral portion wt-11 

 defined. Abdomen triangular, with nine segments besides a 

 short telson. Abdominal axis broad, with a median ridge; 

 pleurae short and flat Silurian ; England. 



Bunodella, Matthew. Cephalothorax .-mall, alNluminal 

 segments seven, acute. Axial portion of tin- lidy |irtmiinrnt : 

 telson not observed. Silurian ; New Brunswick. 



Pseudoniscus, Nieszk. Body oval ; cephalothorax short, 

 with broad central portion and large compound eyes; nim- 

 trilobed abdominal segments besides a short caudal spine ; th- 

 posterior ones nearly parallel with the telson. Silurian : 

 Oesel. 



Order 3. EUBYPTERIDA. Burmeister. 



(Grigantostraca, Haeckel.) l 

 Body elongated, with a thin chitinous epidermal skeleton 



i in-;. 



ll< i/i iaspis limuloidrt, 

 Woodw. Silurian; l..-int- 

 wardine, England. Vi (aft-r 

 Woodward). 



ornamented by fine scale-like markings. Cephalothorax usually 



with two large faceted lateral eyes and a pair of median ocelli; on the ventral /<' 



six pairs of legs, of which the first is preoral and chelate. Mouth bordered posteriorly by 



a metastoma, and anteriorly by an epistoma, both simple plates. Abdomen thirteen- 



jointed, the anterior six segments bearing ventrally five pairs of broad, leaf-like apj>nn/nii>.< 



(apparently comparable to the operculum and branchial appendages of Liiindu.*). The 



posterior six segments annular, without appendages ; telson sometimes spatula.!'- in ahape. 



This order, which is restricted wholly to the Palaeozoic, embraces the largest Arthropods 

 known, some of them (Pterygotus, Stylonurus) having attained a length of over 2 nu-tiv>. 

 The presence of gills upon the branchial appendages shows that in all probability tin- 

 Eurypterids were aquatic, and the structure of their appendages indicates that tli- 

 good swimmers. They are found associated with Graptolites, Cephalopods, and Trilobites in 



1 Literature : 



Dekay, J. ti., On a Fossil Crustacean (Ann. N.Y. Lyceum Nat. Hist., I.), 1825. /,' / . 



Ueber em Eurypterus (Palaeoutogr., I.), 1848. M'Coy, F., Classification of some BritVi 

 Crustacea (Ann. Mag. Nat. Hist. [2], IV.), 1849. Huxley, T. H., On Himantopterus (Quar. Journ. 

 Geol. Soc., XXL), 1856. Idem, and Salter, J. W., On the Genus Pterygotus (Mem. Geol. Surv. 

 United Kingdom Mouogr., L), 1859. Page, !>., Advanced Text-Book of Geology, 1856 and 1859. 

 Nieszkowski, J., De Euryptero remipedo. Dorpat, 1858. (Also in Arch. Naturgesch. Liv.-Esth.- 

 und Kurlauds, II.), 1859. Hall, J., Palaeontology of New York, III., 1859. Stilts; J. U .. 

 Papers in Quar. Journ. Geol. Soc., XIX., 1863. ir/W'v/v/, //., Numerous Papers in (U-ol. M 

 1864 ; IX., 1872 ; Quar. Journ. Geol. Soc., XXL, XXIV., XXVII.. XX \ MI.. , 

 Monograph of the British Fossil Crustacea of the Order Mi-m-tumata (Palaeont. Soc.), 1866-78. 

 Grote, A. R., and Pitt, W. H., New Species of Eusarcus and 1'terygotus (Bull. Buffalo Soc. Nat 

 ScL, III.), l875.Pohlm/<, J., Fossils of the Water-Lime Group (ibid. IV.. V.), 1882-97. 

 B. Jv., Further Researches among Crustacea and Arachnida (Trans. Roy. Soc., Edinburgh, \.\.\. . 

 1882. Schmidt, F., Miscellanea Silurica, III. (M.-m. A.-ad. Imp. BcL, St. IV-tt-rsb. [7J, XX XI. . 

 1883. Hall, J., Second Geol. Surv. iVnusylvania, K p. 1'IT. 1884. Whit 

 Fossils of Canada, III., Pt. 1, 1884. Hall, J., and Clarbe,J. M.. l';d:i.-Mnt..lo_'y ..f N.-w York, VII.. 

 1888,Claypole, E. W., On Carcinosoma, etc. (Amer. Geol., VI., XIII.), 1890-94. /V,///i/, ./.. 

 Eurypterides uouveaux du Devonien (Ann. Soc. Geol. Belg., XVII.), 1890. Laurie, M., Eurypterid 

 Remains from Pentland Hills (Trans. Roy. Soc., Edinburgh, XXXVII.), 1892. Anatomy and Rela- 

 tions of Eurypterida (ibid.), XXXVIII.), 1893. Recent Additions to Knowledge of Kurypu-rida 

 (Nat. Sci., III.), 1893. Whit/i.-/,/, 11. J'., Report Geol. Survey of Ohio, VII., 1893. // 

 Neue Bearbeitung des Eurypterns P'ischeri (Bull. Acad. Imp. Sci.. St. IV-tersb. [o], IV.), 1896. 



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