226 THE HABITAT OF THE EURYPTERIDA 



two fragments. The carapace looks as though it might well belong 

 to a large Hughmilleria; at any rate it has no close affinities to any 

 other species. Similarly, little of correlative value can be deduced 

 from Stylonurus multispinosus which is known only from a group of 

 endognathites. In their characteristics they are different from any- 

 thing in the Bertie (39, 297), and are of little relational value. 



It will be shown below (p. 232) that E. pittsfordensis is closely 

 related to E. lacustris in the Bertie, but as will be seen, this is entirely 

 expectable. 



In the Shawangunk fauna the most abundant species is Hugh- 

 milleria shawangunk whose relationship has been discussed under the 

 Pittsford fauna. The very rare forms, Eusarcus (?) cicerops, Doli- 

 chopterus stylonuroides, Stylonurus my ops, and Pterygotus globiceps, 

 represented by only a few fragments, show no particular relation to 

 species in any other fauna. Indeed, a comparison of the young of 

 E. scorpionis with the young of E. cicerops shows that the cephalon 

 was very different in outline and the position of the eyes was not at 

 all similar (Clarke and R., 39). Similarly, Stylonurus cestrotus, found 

 only in a fragmentary condition, "stands apart from all its allies in a 

 number of characters that show it to be an aberrant form" (39, 291) 

 Eurypterus maria, of which many young and one or two mature indi- 

 viduals have been found, is "greatly different from all its American 

 congeners," (39, 190). The relations of Dolichopterus otisius have 

 already been pointed out, and it has been shown that while it agrees 

 in certain characteristics with one species, in others it agrees with a 

 different one, so that its affinities cannot be said to be with any par- 

 ticular fauna. 



Summarizing the evidence offered in a comparison, species by 

 species, it becomes clear that the dominant, most abundant species in 

 the Pittsford and Shawangunk faunas are alike and that there is 

 only one form in either of these which shows relationship to a Bertie 

 species. 



Summary of Facts of Distribution on Continent of Appa- 

 lachia. The following points may be briefly recapitulated: 1. In 

 the sediments which it has been demonstrated (by myself or others), 

 were with more or less certainty derived from Appalachia, the 

 eurypterids are either unique, showing no relation to known species 

 in North America or other continents, or else they show phyletic 

 relationship inter se, the species of later faunas having certain char- 

 acteristics in common with those of (generally the mature forms of) 

 earlier faunas. 



