Il8 NEW YORK STATE MUSEUM 



been left out of consideration in discussions of the Lower Siluric 

 faunas. Hall's type, which was kindly loaned to us by Dr E. O. 

 Hovey, proved, from gutta-percha squeezes, to be specifically iden- 

 tical with the specimens in our collection from Snake hill and also 

 with the other specimen formerly described by us as C y p h a s p i s 

 hudsonica. We have here (plate 9, figure 2) introduced 

 a new figure of the original of Olenus undulostriatus 

 from a gutta-percha squeeze. 



While Hall referred his species to Olenus and Miller placed the 

 same under Elliptocephala, Whitfield and Hovey in the catalog of 

 palaeontologic types of the American Museum of Natural History, 

 have cited that type as B a t h y u r u s sp. 



We had placed the cranidia from the Rysedorph Hill conglomerate 

 and of Green island with Cyphaspis on account of the form of the 

 glabella and the large basal lobe. From inspection of the whole 

 carapace and the thorax we have however become convinced that 

 those species should be more properly referred to Proetus, the 

 isolation of the basal lobe being too indistinct for Cyphaspis and 

 the carapace relatively too broad and the glabella not prominent 

 enough. On the other hand, while we recognize the similarity of 

 the carapace of P. undulostriatus to that of Bathyurus in 

 its former generalized conception, we doubt that this genus, as 

 characterized by its genotype, B . e x t a n s (Hall), could be made 

 to receive forms like the present with a distinct thick anterior 

 margin and a much broadened base of the glabella through a more 

 or less prominent basal lobe. All these are features characteristic 

 of Proetus and are becoming still more emphasized in Cyphaspis, 

 but absent in Bathyurus. 



Proetus matutinus Ruedemann from the Rysedorph Hill 

 conglomerate is obviously a closely related older form, the black 

 pebbles being probably of Black River and the Snake Hill beds of 

 Trenton age. It is mainly distinguished by the broader frontal limb 

 of the cranidium. The glabella is also distinctly more convex, but 

 this may be due to the preservation in limestone, the shale fossils 

 always being more or less flattened. The fine anastomosing sculp- 

 ture lines are identical in P. undulostriatus and 

 matutinus. 



In New York State Museum Bulletin 42, 1901, page 536, the 

 present writer has cited from the '' Middle Trenton shales," exposed 

 at the Brothers quarry at South Troy, Proetus parvius- 

 c u lu s Hall, from a cranidium collected by him at that locality. 



