THE UPPER SILURIAN OF NORTH AMERICA. 61 



This rock is very nearly on the horizon of the lowest Devonian of 

 Europe, in which corresponding ichthyic remains are well known." 



Professor Eogers goes even further and adds, " It must be enun- 

 ciated as a general fact that hitherto no traces have been discovered of 

 any vertebrate animal whatsoever during all those earlier Palaeozoic 

 ages which are embraced in the Cambrian and Silurian periods of the 

 English geologists, or the equivalent Primal, Auroral, Matinal, 

 Levant, Surgent, and Scalent periods according to the nomenclature 

 of the Pennsylvania Survey "*. 



To reconcile these quotations is difficult. Professor Rogers could 

 not well have forgotten seeing fish-scales in the Scalent and Surgent 

 groups had he really done so. Such forgetfulness would be especially 

 difficult to one who believed that even in Europe no fish-remains of 

 that date were known. Sir Charles Lyell's character for accuracy is 

 too well known to need assertion. It is possible that Professor Eogers 

 saw the scales, for they were there. It is also possible that Sir C. 

 Lyell's memory was at fault. Altogether it is a rather singular 

 example of divergence between the statements of two eminent 

 geologists. 



Description of the Species. 



Onchtjs pennstlvanictjs, sp. n. (Eig. 5.) 



Spine, when complete, about half an inch long, with a diameter 

 at base of about one eighth of an inch, very slightly curved and con- 

 sisting of an inner core (perhaps only composed of material filling 

 an original cavity) and an outer sheath. The outer portion shows 

 a fluted surface, with eight ridges in the quarter of the circumference 

 which is visible ; ridges rounded, their height being about half their 

 breadth ; the furrows between them acute at base and formed merely 

 by the edges of the two ridges without any breadth. 



Locality and horizon. Perry county, Pennsylvania, in the Bloom- 

 field Sandstone or uppermost member of the Onondaga Yariegated 

 Shales. 



Eig. 5. — Onchus pennsylvaui- Fig. 6. — Onchus clintoni. 

 cus, showing fluted surface 

 and core. 



Onchus clintoni, sp. n. (Eig. 6.) 



Spine slightly curved, the part visible about half an inch long and 

 showing on the one side 5 rounded low ridges meeting each other 



* This statement appeared in 1858. 



