PLATE 12 
Eurypterus lacustris Harlan 
Page 173 
See plates 9-11, 13 
t Chelicera. x 3 
Anterior portion of a female opercular appendage, showing the two 
tubular lateral appendages, the test of the operculum being broken 
away. X 2 
Eurypterus lacustris var. pachychirus Hall 
Page 179 
See plate 19, figure 1 
3 Hall’s original in Palaeontology of N. Y., v. 3, pl. 82, fig. 1. The abdomen 
is somewhat distended and the sculpturing well shown. 
The figures are from photographs. All specimens are from the Bertie 
waterlime at Buffalo, Erie co., N. Y. The originals of figures 1 and 
2 are in the museum of the Buffalo Society of Natural Sciences, that of 
figure 3 in the State Museum 
464 
