CLASS ir ARACHNIDA— XIPHOSURA 773 



centre in front. First pair of appendages chelicerate. Metastoma with two small 

 accessory 2)Iates. Abdomen tvith seven to ten segments, which are dorsally free or 

 coalesced ; the six anterior ones provided with lamellar appendages on the under side. 

 Telson long, ensiform, movable. 



Family 1. Oyclidae Packard. 



Cephcdothorax small, orbictdar, discoidal or convex, calcareous or chitinous, 

 bounded by a distinct border. Cephalic appendages nearly as in embryonic Limulus. 



Cyclus de Kon. (Fig. 1497). Known almost solely by the orbicular 

 cephalothorax with its imperfectly preserved appendages, which seem to be 

 simple swimming legs. Their enlarged joints cover the 

 ventral surface of the carapace everywhere except in 

 the centre, which is occupied by a V-shaped plate, 

 towards the pointed extremity of which all the basal 

 joints of the limbs converge. Coal Measures ; Great 

 Britain, Illinois and Missouri. 



Family 2. Belinuridae Packard. 



■ Body limnloid in^ general aspect. Cephalotltorax F'*'- ^^'•^'•■ 



rounded, with long, slender genal spines; its appendages as coafMeasm^'fSm Creek; 

 in larval Limulus. Abdomen with the segments in vart n'inois. cephaioUiorax show- 



, , 7 77 T 1 , 1 . 1 J- -77 7 n ^ ing traces of let;s and alimentary 



or almost wliolly consolidated ; telson of variable length. canal, i/i- 



Belinurus Konig (Fig. 1498). Cephalothorax hippocrepiform, its central 

 portion surrounded by a broad, flat marginal area, which at the genal angles 

 is produced into a long, slender spine. Abdomen with eight segments, 

 besides the much-elongated, slender telson ; seventh and eighth segments are 

 consolidated. Upper Old Red Sandstone and Coal Measures of Great Britain 

 and northern France {B. belkdus Konig ; B. reginae Baily). Also in Coal 

 Measures of Illinois (B. lacoei Packard). 



— Baily, W. IL, Explanation of Sheet 137 of the Maps of the Geol. Surv. Scotland, 1859.— 

 Remarks on Beliuiirus. Ann. Mag. Nat. Hist., 1863, ser. 3, vol. xi. — Giebel, O. G., Limulus 

 Decheni. Zeitschr. gesammt. Naturw., 1863, vol. xxi. — Meek, F. B., and Worthen, A. H., Kept. 

 (tboI. Surv. III., 1868, vol. iii. — Woodivard, H., Notes on Neolimulus, Cyclus, Merostomata, etc. 

 Geol. Mag., 1869-94, dec. 1, vol. v. ; dec. 3, vols, vii., ix. ; dec. 4, vol. i. — Dohrn, A., Embryologie 

 und Morpliologie des Limulus. Jenaische Zeitschr., 1871, vol. vi. — Packard, A. S., Development 

 of Limulus. Mem. Boston Soc. Nat. Hist., 1872, vol. i. — Idem, Anatomy, Histology and 

 Embryology of Limulus. Anniv. Mem. Boston Spc. Nat. Hist., 1880. — Idem, Carboniferous 

 Xiphosurous Fauna of North America. Mem. Nat. Acad. Sci., 1885, vol. iii. — Van Beneden, 

 M. E., Systematic Position of King Crabs and Trilobites. Ann. Mag. Nat. Hist., 1872, ser. 4, 

 vol. ix. — Milne-Edwards, A., Recherches sur I'anatomie des Limules. Ann. Sci. Nat., 1873, 

 ser. 5, vol. xvii. — Lankester, E. R., Limulus an Arachnid. Quart. Journ. Microsc. Sci., 1881, 

 vol. xxi. — Peach, B. N., Further Researches among Crustacea and Arachnida. Trans. Roy. Soc. 

 Ediub., 1882, vol. xxx. — Williams, H. S., New Limuloid Crustacean from the Devonian. Amer. 

 Journ. Sci., 1885, ser. 3, vol. xxx. — Hall, J., and Clarke, J. M., Palaeontology of N.Y., 1888, 

 vol. vii. — Kishenouye, K., Development of Limulus. Journ. Coll. Sci. Tokyo, 1891, vol. v. — 

 Kingsley, J. S., Embryology of Limulus. Journ. Morphol., 1892-93, vols, vii., viii. — Fritsch, 

 A., Fauna der Gaskohle. Prague, 1901, vol. iv. — Clarke, J. M., Pseudoniscus in the Eurypterus 

 Beds of New York. Rept. N.Y. State Palaeont. for 1900. (54th Ann. Rept. N.Y. State Mus.), 

 1902. — Rogers, A. F., Some new American Species of Cyclus from the Coal Measures. Kansas 

 Univ. Sci. Bull., 1902, vol. i.. No. 10. — Stromer von Reichenbach, E., tJber Molukkenkrebse. 

 Zeitschr. Deutsch. Geol. Ges. Mouatsber., 1907, vol. lix. — Gaskell, W. B., Origin of the 

 Vertebrates, London, 1908. — Patten, W., Evolution of the Vertebrates and their Kin, 1912. 



