Pala'ozo/c H'txtoi'ij (if Feiiii^iilrdiiia. — CJanjxile. 159 
R. eumberlandiie. 
R. intermedia. 
R. raarylandica. 
R. ovalis. 
R. ovoides. 
R. suessana. 
Lower Helderberg R. aequiradiata. 
R. elliptica. 
R. Isevis Hall. 
R. mutabilis. 
R. portlandica. 
Prof. Hall has recently taken his R. johanni from its old posi- 
tion and has made it the tj-pe of a new genus Newherrii., charac- 
terized by the slightness or absence of external radial striation of 
the two strong dental plates, and the thick hinge plate and inter- 
nal loop of Rensselcsria. To this new genus is also referred the 
R. hevis of Meek which is reported b}' Whiteaves from several 
places in the Mackenzie River district.* 
When the writer, at the meeting of the Am. Ass. for the Adv. 
of Science at 3Iinneapolis, in 1883, announced his discovery of 
these fossils in the Hamilton sandstone, he spoke of the difficulty 
which he had felt in separating them from some of Prof. Hall's 
species, such as R. marylandica and R. johanni. He was not 
willing in this state of uncertaint}' to coin a new name and left the 
matter in doubt. These fossils are now in the hands of Prof. 
Hall for description and the difficulty will doubtless be cleared up. 
It may very probably prove that the}- will also belong to the new 
genus Newberria from their close resemblance to R. johanni. 
AVhether this should prove to be the case or not, the^' will at an^- 
rate carr}' this type of shell up from the Corniferous limestone to 
the middle of the Hamilton. 
The last name on the list also calls for a short notice. It is a 
cast of the dorso-inedian plate of Coccosfens or some nearly allied 
placoderra, but its exact relationship has not yei been determined. 
Its occurrence in these beds is interesting because, so far as I am 
aware, no fish fossil has yet been described from the Hamilton 
group in Penns^dvania, though a scanty fish fauna has come to 
light from the rocks of similar age in adjoining states. At some 
future time more details may be given regarding this solitary 
specimen. 
*See Contributions to Canadian Paiiconiology, "Vol. I, pt. 3. 
