1 SYNOPSIS OF GENERA. 



1856. Lesmahago, Mubchisojj. Quart. Journ. Geol. Soc 



Himantopterus, Salter. Quart. Jour. Geol. Soc. 



Eurypterus, Banks. Quart. Jour. Geol. Soc. 

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Page. Advanced Text-book of Geology. 



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1864. Eurypterus, Woodward. British Assoc. Rept. 

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1868. Eurypterus (Anthraconectes), Meek and Wokthen. Amer. Jour. Sri. Mir,.. 

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1868. Eurypterus, W iward. Quart, -lour. Geol. Soc. 



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1870. / , W ward. British Assoc. Rept. 



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Diagnosis. Body elongate. Cephalon about one-fifth the length of the body, 

 sub-quadrate in outline, gently convex. Eyes large, reniform, situated some- 

 what anteriorly, and within them lie two ocular punctoe or ocelli. Oral aperture 

 surrounded by five pairs of cephalic appendages, in front of which is a pair of 

 minute antennules. 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 i 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 lirst two bearing median processes extending posteriorly. The 

 first segmenl also hears a series of symmetrically arranged median plates, which 

 may be connected with the genital apparatus. Post- abdomen composed of six 

 tapering segments ami a long slender caudal spine. 



