THE EURYPTERIDA OF NEW YORK 221 
of the genus and in this evidence of waning racial characters it invites 
special recognition. The Pennsylvania species to which we have referred 
are E. mansfieldi C. E. Hall, E. pennsylvanicus C. E. 
Hall, E. stylus J. Halland E. approximatus Hall & Clarke.’ 
These species, together with E. (Anthraconectes) mazon- 
ensis are distinguished from Eurypterus proper by the following features: 
(1) the character of the spines of the endognathites,? seen in E. mans- 
fieldi, in E. mazonensis and E. stylus,® (2) the develop- 
ment of the scales into mucros, giving the greater portion of the surface a 
spinous appearance. This tendency to spinosity, especially of the posterior 
margins of the abdominal somites is also present in 
British Carbonic forms, as is amply evidenced by 
E. scouleri Woodward‘ with its long pointed 
scales, E. (?) stevensoni R. Etheridge jr [Geol. 
soc. Lond. Quar. Jour. 1877. 33:223] in which the 
surface 1s covered with long blunt spines and scales, 
giving it the appearance of a mass of congealed drops, Figure 48 | Euryp- 
while in E. scabrosus H. Woodward‘ the scales ensoni bitensne. 
have become prominent wartlike tubercles, inter- Pits _axd__ scales. 
oo (From Etheridge) 
spersed with disklike bodies which proved to be 
“calculi” or bodies of globular calcite formed inside the integument. All 
these excrescences are distinctly phylogerontic and seem to indicate that 
‘The first two are described in the Proceedings of American Philosophical Society, 
volume 7, 1877, and Second Geological Survey of Pennsylvania, Report of Progress, 
PPP, 1884, page 31 et seg. E. stylus is described in the last named publication 
and E. approximatus in the Palaeontology of New York, volume 7, 1088, 
explanation of plate 27, figure6. E. potens Hall is not described and the figures 
[Penn. Rep’t, pl. 4, fig. 9, 10] indicate that it is based on unrecognizable fragments. 
2 See Appendix. 
*In E. pennsylvanicus and E. approximatus the endognath- 
ites are not preserved. The former species is based on a single carapace. 
‘Pal. Soc. 1872. v. 26, pl. 25-27. 
®Geol. Mag. n. s. 1887. dec. 3, 4: 481. 
