1 
SYNOPSIS OF GENERA. 
1856. Lesmahago, Murchison. Quart. Journ. Geol. Soc. 
1856. Himmitopterus, Salter. Quart. Jour. Geol. Soc. 
1856. Eurypterus, Banks. Quart. Jour. Geol. Soc. 
1858. Ewrypt&i'us, Salter. Quart. Jour. Geol. Soc. 
1859. E^irgpterm, Page. Advanced Text-book of Geology. 
1859. Etirypterus, Dolichopteras, Hall. Palaeontology N. Y., vol. ill. 
1859. Euryptems, Huxley an<l Salter. Mem. Geolog. Surv. United Kingdom. 
1859. Eurypterus. Nieszkowski. Archiv. fiir Naturkunde Liv, Est und Kurlands. 
1863. Eurypterus, Salter. Quarterly Journal. Geol. Soc. 
1864. Eurypterus, Woodward. Bi-itisli Assoc. Kept. 
1864. Eurypterus, Woodward. Geological Magazine. 
1868. EurypteribS {Anthraconectes), Meek and Wortuen. Anier. Jour. Science. 
1868. Eurypterus (Antliraconecte.s), Meek and Worthen. Geol. Surv. Illinois, vol. iii. 
1868. Eurypterus, Woodward. Quart. Jour. Geol. Soc. 
1869. Pterygotus, Baily. Brit. Assoc. Kept. , 
1870. Eurypterus, Woodward. Biatisli Assoc. Ilept. 
1871. Eurypterus, Woodward. Quart. Join-. Geol. Soc. 
1871. Eurypterus, Woodward. Trans. Woolbope Club. 
1872. Euryptenos, Barrande. Syst. Sil. du Centre de la Boheme. Suppl. 
1872. Eurypterus, Woodward. Monogr. Brit. Poss. Merostomata. 
1876. Eurypterus, C. F. Boi.MER. Lethaea palaeozoica. 
1877. Eurypterus, Doliehopterus, C. E. Hall. Trans. Amer. Philos. Soc. 
1882. Eurypterus, Pohlman. Bull. Buffalo Soc. Nat. Sci. 
1882. Eurypterus, Whitfield. Descr. New Species Fossils from Ohio. 
1884. Eurypterus, Hall. Eurypteridae Devon, and Carbonif. Format. Penna. Kept. P 3. 
1884. Eurypterus, Whiteaves. Geol. and Nat. Hist. Surv. Canada. Palseoz. Fossils. 
1887. Eurypterus, Woodward. Geological Magazine. 
Diagnosis. Body elongate. CepJialon about one-fifth the length of the body, 
sub-quadrate in outline, gently convex. Eyes large, reniforin, situated some¬ 
what anteriorly, and within them lie two ocular punctee or ocelli. Oral aperture 
surrounded by five pairs of cephalic appendages, in front of which is a pair of 
minute antennnles. The first three pairs of appendages or gnathopods are of 
approximately the same length, the joints of the fourth pair being more elon¬ 
gate and the fifth pair being developed into powerful swimming appendages, the 
last two segments of which are very broad and Hat. Behind the mouth lies an 
oval plate {Metastoma). Abdomen upon the dorsal side composed of six segments, 
the first of which corresponds to the operculum of Limulus. Upon the ventral 
surface there are but five segments apparent, all of which are divided by a median 
suture, the first two bearing median processes extending posteriorly. The 
first segment also bears a series of symmetrically arranged median plates, which 
may be connected with the genital apparatus. Post-abdomen composed of six 
tapering segments and a long slender caudal spine. 
