LOWER SILURIC SHALES OF THE MOHAWK VALLEY 



The same is now packed away and at present not accessible, but the 

 writer feels sure that this cranidium also belongs toP.undulo- 

 s t r i a t u s from his recollection of the minute fossil and from the 

 fact that P. parviusculus is clearly a very close relative 

 of P. undulostriatus. The small specimen from Troy 

 was exfoliated and therefore failed to show the striae. 



P. parviusculus in size and outline of carapace and glabella 

 would appear to be difficult of differentiation from the Snake Hill 

 species. The fact that its surface is described as " smooth, or very 

 finely granulose " would seem to furnish a distinctive character. 



Beecher (1895, p. 174) states, however, regarding the surface 

 sculpture of this species : " In the original description of this 

 species, no mention was made of fine undulating striae ornamenting 

 the entire dorsal surface of the test, nor of the basal lobes of the 

 glabella. Both these features are present in the type specimen, which 

 is from Cincinnati, Ohio, as well as in all the specimens from the 

 Utica slate near Rome, New York." 



If it were not for the fact that the cheeks and glabella of the 

 types of P. undulostriatus and P. hudsonicus 

 are relatively broader than those figured of P. parviusculus 

 and the genal spines diverging instead of being subparallel, we should 

 not hesitate to consider parviusculus a synonym of the 

 older term. Since these differential characters in the scant material 

 at our disposal and especially in the type specimen may be due 

 to longitudinal compression, it is possible that later collections will 

 demonstrate the identity of the Cincinnati and Snake Hill forms. 

 At any rate, if different, they are very closely related. 



The species here described presents in its outline great similarity 

 to Proetus latimarginatus Weller from the Jackson- 

 burg limestone of New Jersey. The latter type is however described 

 as possessing a finely granulose surface. 



Acidaspis crossota (Locke) 

 PL 9, figs. 4, 5 



A small Acidaspis from the Indian Ladder beds, represented by a 

 cranidium and several fine cheeks, has been identified by Doctor 

 Ulrich with Acidaspis crossota Locke, a form hitherto 

 known only from the Cincinnati group of the neighborhood of 

 Cincinnati. It is recorded by Nickles as ranging through the Eden 

 (" Utica ") shale of Cincinnati. 



