20 North American Palseozoic Crustacea. 



pulex, Hall & Clarke, 1888; Pal. New York, vol. 7, p. 206, pi. 35, 



figs. 10, 11. 

 pulex, Etheridge, Woodward & .Tones, 1888 ; 6th Rept. Comm. Fossil 

 Phyllopoda Pal. Rot-ks, p. 9. 

 Enproops, Meek, 1867 ; Am. Jour. Sci., 2d Series, vol. 34, p. 394. See Belinurus 



and Prestwichia. 

 Eurypterus, De Kay, 1825 ; Annals Lyceum Nat. Hist, N. Y., vol. 1, pt. 2, 

 p. 375. 

 Diagnosis. — Body elongate. Cephalon about \ the lengtli of tlie body, 

 subquadrate in outline, gently convex. Eyes large, reniform, situated 

 somewhat anteriorly, and within them lie two ocular punctre or ocelli. 

 Oral aperture surrounded by 5 pairs of cephalic appendages in front of 

 which is a pair of minute antennules. The first 3 pairs of appendages 

 or gnathopods are of approximately the same length, the joints of the 

 4th pair being more elongate, and the 5th pair being developed into 

 powerful swimming appendages, the last two segments of which are 

 vary broad and flat. Behind the mouth lies an oval plate (metastoma). 

 Abdomen upon the dorsal side composed of 6 segments, the first of 

 which corresponds to the operculum of Limulus. Upon the ventral 

 surface there are but 5 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 6 tapering segments and a 

 long slender caudal spine. (Hall & Clarke, 1888 ; Pal. New York, 

 vol. 7, p. 1.) 

 Beecheri, Hall, 1884; 2d Geol. Survey Pennsylvania, vol. PPP, p. 30, 

 pi. 3, fig. 1. Chemung. 



Beecheri, Hall & Clarke, 1888 ; Pal. New York, vol. 7, p. 156, pi. 27, fig. 5. 

 Beecheri, Etheridge, Woodward & Jones, 1888; Gth Rept. Comm. Fossil 



Phyllopoda Pal. Rocks, p. 9. 

 Boylei, Whiteaves, 1884; Pal. Fossils, vol. 3, pt. 1, p. 42, pi. 7, fig. 3. 



Guelph. 

 DeKayi, Hall, 1859; Pal. New York, vol. 3, p. 411*, pi. 82, fig. 1. 



Waterlime. 

 Eriensis, Whitfield, 1881 ; Annals New York Acad. Sci., vol. 2, p. 196. 



Lower Helderberg. 

 Eusarcus fjramUs, Grote & Pitt, 1875 ; Bull. Bufifalo Soc. Nat. Sci., vol. 3, p. 17. 



Waterlime. 



Referred by J. Pohlman (Bull. Buffalo Soc. Nat. Sci., vol. 5, p. 31) to 



Exirypterus scorpionis. An almost similar term, E. scorpioides, was used 



for a species of this genus by H. Woodward in 1868 ; we suggest that 



of E. Poldmani for this species. 



giganteus, Pohlman, 1882; Bull. Buffalo Soc. Nat. Sci., vol. 4, p. 41, 



pi. 2, fig. 1. Waterlime. 



lacustris, Harlan, 1834; Trans. Geol. Soc. Pennsylvania, vol. 1, p. 98, 



pi. 5, fig. 2. Waterlime. 



