LOWER SILURIC SHALES OF THE MOHAWK VALLEY 117 



for some time. It is the only example of this species known to us 

 from the Schenectady beds and appears to agree in all essential 

 characters with the Trenton type. The fact that it is narrower and 

 higher is due to lateral compression. 



Proetus undulostriatus (Hall) 

 PI. 9, fig. 2, 3 



Olenus undulostriatus Hall. Pal. N. Y., 1847, 1 1258, pi. 67, fig. 

 3a, b. 



Cf. Proetus parviusculus Hall. I3th An. Rept. N. Y. State 

 Mus. Nat. Hist., 1860, p. 120. 



Elliptocephala undulostriata S. A. Miller. North Amer. 

 Geol. & Pal., 1889, p. 546. 



Bathyurus sp. Whitfield & Hovey. Bui. Amer. Mus. Nat. Hist., 

 pt. i, 1898, ii 170, 71. 



Proetus parviusculus Ruedemann. N. Y. State Mus. Bui. 42, 

 1901, p. 536. 



Cyphaspis hudsonica Ruedemann. N. Y. State Mus. Bui. 49, 

 1901, p. 64, pi. 4, figs. 8, 9. 



The writer described in 1901 several small cranidia from the 

 black limestone pebbles from the Rysedorph Hill conglomerate 

 which are especially characterized by a fine system of transverse or 

 concentric sculpture lines, as Cyphaspis matutina, and 

 another cranidium of broader habit from the supposed Upper Utica 

 shale of Green island as C. hudsonica. Collecting in the 

 Snake Hill beds at Snake hill furnished a few years ago a cranidium 

 (plate 9, figure 3) which not only exhibits the identical charac- 

 teristic sculpture of C. matutina but also resembles it in all 

 other features with the exception that it is a little broader and the 

 frontal limb distinctly narrower. In the latter features it fully 

 agrees with the C. hudsonica which comes from beds which 

 we now know to be identical with the Snake Hill beds. This latter 

 specimen proves on reinvestigation to be exfoliated, for which 

 reason the surface sculpture is not observable while the glabellar 

 furrows are more distinct. 



Hall had in 1847 described and figured as Olenus undulo- 

 striatus from the " Hudson River group " of Snake hill, the 

 mold of a carapace and part of the thorax of a trilobite which since 

 that author had referred in his early work a considerable number 

 of Lower Cambric fossils to the " Hudson River group," had also 

 been placed by catalogers in the Cambric, or rather since the original 

 description is very brief and the figure quite unsatisfactory, it has 



