PLATE XXVII. 
Protolimulus Eriensis. 
Rage 163. 
Fig. 1. A view of the ventral surface from the original cast in sandstone, showing the condition of j)reserva- 
tion of the dilferent parts. 
Chemung group. LeBoeuf, Bh'ie county, Peimfiylvania. 
Fig. 2. A diagram of the same : 
cd. Cephalic doublure. 
s. Genal spines. 
X. Hypostoma (?), or axial angulation of cephalic doublure, 
m. Position of mouth, 
ca. Cephalic appendages. 
f. Foliaceous terminations of the last pair of cephalic ajipendages. 
' tp. Thoracic plate. 
r. Longitudinal abdominal I'idges. 
m. Marginal abdominal spines. 
t. Telson. 
Eurypterus prominens. 
Page 157. 
Fig. 3. The cephalon, showing the prominent and anteriorly situated eyes, the ocelli, the flattened doi'sal 
surface, and the oblique postero-lateral pits. 
Fig. 4. Profile view of the same, showing the elevation of the shield, the jiosition of the eyes and the 
extension of the postero-lateral angles. 
Clinton group. From the northwn ■part of Cayuga county. 
Eurypterus Beecheri. 
Page 15G. 
Fig. 5. Doi'sal view of the original specimen, showing the form of the body, the number, size and orna¬ 
mentation of the somites, and portions of the large swimming appendages. The drawing is 
made from a plaster cast taken from a natural mould of the dorsal surface. 
Chemung gi'oup. Wan-en, Warren county, Pennsylvania. 
Eurypterus approximatus, n. sp. 
Fig. 6. Doi'sal view of the original, showing the cejihalon and nine somites, also the conspicuous marginal 
spines and the characteristic ornamentation of the surface. 
Waverly group. Three miles south of Warren, Warren county, Pennsylvania. 
This species differs from E. Pennsylvanictis, C. E. Hall, in the absence of genal spinules and con¬ 
spicuous nodes on the posterior margin of the cephalon, and in the more closely appressed 
eyes. In E. Mansfieldi, C. E. Hall, from the Coal Measures, the cephalon is longer, the eyes 
more distant, and the abdominal segments scarcely as broad. 
