This is the first stage in which the fine transverse sculpture lines could be recognized [pl. 64, fig. 5].
Horizon and locality. This species is one of the most common forms in the fauna of the Shawangunk grit at Otisville, N. Y.
Remarks. H. shawangunk differs from the genotype in its smaller size, somewhat broader carapace and most distinctly in the surface sculpture which is characterized by parallel, transverse striae, absent in the other species.
Genus PTERYGOTUS Agassiz
Pterygotus will always be historically associated with the rocks of Scotland which carried the "seraphim" of the quarrymen, the type 
Figure 70 Restorations of Stylonurus powriei (1) and Pterygotus anglicus (2) in Page's Introductory Text-book of Geology. ed. 5. 1859. p. 71 of Agassiz's P. anglicus, and later afforded the material for the monographs by Huxley and Salter [1859] and by Woodward [1866]. The British rocks have altogether yielded nine species of Pterygotus, two of which, P. anglicus and P. bilobus, are known in complete specimens. The fragments of several of these species have left no doubt that the individuals attained gigantic proportions and surpassed all other then known Merostomata in size. Schmidt's work [1883] on the merostomes of the Eurypterus beds of Oesel contains a very elaborate description of the Pterygotus, P. osiliensis, and corrects several misconceptions of the preceding authors in regard to the structure of the genus. Above all it established the number of walking legs to be four pairs, Woodward having assumed but three, and it recognized the proper position of the epistoma. Ten years after Schmidt's publication
