348 NEW YORK STATE MUSEUM 
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 
of Agassiz’s P. anglicus, 
and later afforded the material 
for the monographs by Hux- 
ley and Salter [1859] and by 
Woodward [1866]. The British 
rocks have altogether yielded 
nine species of Pterygotus, 
two of which, P. angli- 
cus and P. bilobus, 
are known in complete speci- 
Figure 7o Restorations of Stylonurus powriei 
(1) and Pterygotus anglicus (2) in Page’s mens. The fragments of sev- 
Introductory Text-book of Geology. ed. 5. 1859. p. 71 eral 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 des- 
cription 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 
