2 A patch of integument with finely preserved sculpture, identical with that ascribed here to Stylonurus sp. a and represented on plate 53, figures 10-12
3 Stylonurus cf. myops. Fragmentary medium sized carapace
4 Coxa, probably belonging to Hughmilleria
5 Small telson of an Erettopterus
182 B 23 has afforded a carapace showing the position of the eyes, and not distinguishable from Eurypterus maria. 182 C 4x contains:
1 Eurypterus maria. Large and small carapaces
2 Dolichopterus cf. otisius. Medium sized carapace
3 Stylonurus myops. Large and small carapaces
4 Hughmilleria shawangunk. Large carapace
5 Pterygotus cf. globiceps. Small carapace
6 Swimming leg of a Pterygotus or Hughmilleria
These faunules are so similar in their aspect and composition to that of the Shawangunk grit at Otisville, that, although they are too fragmentary for a conclusive identification, it seems proper to infer that they belong to the same or an approximate horizon. It is, therefore, of much interest that Professor van Ingen has in the Swatara Gap section obtained good evidence that these beds which also correspond to the Shawangunk grit in lithology and stratigraphy, contain marine fossils of much greater age than the Salina. Professor van Ingen states that B8x of his section carries an apparently Clinton fauna, and B19x a Rochester (or Lockport) fauna, while 182 C 4x contains Arthrophycus cf. harlani Conrad. It will be noticed that the fairly good Shawangunk grit fauna, cited from B16h, comes from an horizon between these beds.
Alternative hypotheses are suggested by this recent work; either that the Shawangunk grit is older than Salina age; or in view of the vast thickness of beds of like lithologic character in central Pennsylvania containing the eurypterid fauna of Otisville aspect, these rocks may represent
