620 Prof. E. W. Claypole — Fish-Remains from the TJ. Silurian. 



both containing Eurypterus and Pterygotus. The English Lower 

 Ludlow and the Water-Lime or basal beds of the North American 

 Lower Helderberg are the lowest strata containing these fossils. 

 On both sides of the Atlantic they range from this level upwards 

 into the Devonian. 



The oldest vertebrate fossils yet announced from America are those 

 found in the Corniferous Limestone or Lowest Devonian of Ohio. 

 Possibly the beds at Gaspe on the Gulf of St. Lawrence are some- 

 what lower, as they have yielded Cephalaspis, which is not yet 

 known from Ohio, and Coccosteus, of which Ohio has yielded only a 

 single specimen. No authenticated fish-fossil has yet been announced 

 from the Upper Silurian rocks of America. 



It is true that reports of the discovery of such remains have been 

 published at various times, but investigation has proved them all 

 erroneous. (See "Palaeontology of New York," voh ii. pp. 319, 

 320, pi. Ixxi. ; " American Journal of Science," second series, vol. i. 

 p. 62 ; " Paleeontology of Ohio," vol. ii. p. 262.) 



During my recent work on the Palseontology of Perry county, 

 Pennsylvania, I came upon some fossils which at once suggested 

 relationship to the Ludlow group above described. Among them 

 were a few spines recalling Onchus tewiistriatns, but with some 

 differences. I have named them Onchus Pennsylv aniens. "With them 

 I discovered abundance of specimens bearing a strong resemblance 

 to Pteraspis, but larger, and differing in some other respects. These 

 I have named Glyptaspis {G. elliptica and G. bitruncata). 



Comparing these with Pteraspis, we find them much thinner, not 

 exceeding one-tenth of an inch in thickness ; whereas specimens of 

 Pteraspis in my possession from Cornwall are nearly one-fourth of 

 an inch thick. The striation on both is equally fine, but is rather 

 less regular on the American specimens. Iliese also show no trace 

 of the spine in which the shield of Pteraspis terminates, as shown by 

 Murchison in " Siluria." 



No traces of the English fossil shagreen — Thelodns and SpMgodus 

 — have been found in the Pennsylvanian beds, though it abounds in 

 the Ludlow rocks. 



The fossils were found in a bed of sandstone about 200 feet below 

 the base of the Water-Lime in Perry county, Pennsylvania ; near the 

 top of the great mass of variegated shale composing the Fifth Group 

 of Eogers in the First Survey of Pennsylvania. This shale in New 

 York immediately overlies the Niagara limestone, which is correlated 

 on satisfactory evidence with the Wenlock limestone of England. 

 Ten or twelve species are common to the two beds. 



It seems, therefore, that the great mass of coloured shale, near the 

 top of which these fossils were found, and which is a continuation 

 of the Onondaga group of New York, has no representative in tlie 

 British series, but corresponds to an interval between the Upper 

 Wenlock and the Lower Ludlow. (For details regarding the corre- 

 lation of these beds in Pennsylvania with those in New York, see a 

 paper by the author in " Proc. Amer. Phil. Soc." for 1884.) 



It is consequently a necessary inference that the beds yielding 



