BUFFALO SOCIETY OF NATURAL SCIENCES 225 



slight knowledge of the various faunas we are unable to perceive re- 

 lationships which very possibly exist. Two species, however, do 

 show kinship with known forms. Hughmilleria magna has charac- 

 ters in common with H. socialis and H. shawangunk from the Pitts- 

 ford and Shawangunk, respectively, while Dolichopterus latifrons 

 agrees "closely with D. otisius from the Shawangunk in the posterior 

 contraction of the carapace." Thus, whatever relationship is indi- 

 cated between the species of the Schenectady fauna and .those of 

 later faunas, is to species in the Pittsf ord and Shawangunk, all "three 

 of which formations have elsewhwere been shown to have had their 

 origin in the sediments from Appalachia. Once again, it appears that 

 rivers coming from the same continent have successive faunas more 

 closely related than those from diverse continents. 



Comparison of Pittsf ord and Shawangunk Faunas. The study of 

 the lithogenesis of these two formations has shown that the Pittsford 

 shale is of the same age as the shales in the upper part of the Shawan- 

 gunk (p. 1 01 above), for which reason it is fitting to consider the 

 faunas of the two formations at the same time, especially since the 

 sediments are known to have come from Appalachia in both cases. 

 A comparison of the Pittsford and Shawangunk faunas shows that 

 the two most common species, Hughmilleria socialis from the former 

 and H. shawangunk from the latter are almost identical. In the shape 

 of the body and form of the head the two species closely resemble 

 each other, while the telsons of the two are identical. As one reads 

 through the description of the Shawangunk form he is struck with 

 the constant similarities in the anatomy between this and the Pitts- 

 ford species. For instance, Clarke and Ruedemann say in regard to 

 H. shawangunk: "The metastoma has not been seen well preserved in 

 position, but we refer several metastom as to this species because they 

 possess on the one hand, the form of that in H. socialis, and on the 

 other, exhibit a peculiar, striated ornamentation apparently character- 

 istic of H. shawangunk" (39, 345). Again, "The crawling legs appear 

 to have been both short and slender as in H. socialis" (39, 344). Be- 

 cause of these similarities, it seems not improbable that H. socialis 

 might represent a mature H. shawangunk, especially since no speci- 

 men longer than 8 cm. is known from the Shawangunk, and no speci- 

 men so short as that from the Pittsford, where the individuals are up 

 to 15 cm. in length. 



Of the other five species in the Pittsford, Pterygotus monroensis 

 is of small importance for it is represented by a single carapace and 



