206 Thirty-fifth Eeport on the State Museum. 



liratus, Hall, and Megistocrinus depressus, Hall. Fine gasteropoda are 

 plentiful throughout this and the preceding formations, but are best 

 preserved and obtained in best condition in this limestone. Among 

 the commonest are Pluerotomoria filitexta, Hall, P. Itys, Hall, Macro- 

 cheilus Hamiltonice, Hall, Platyostoma lineata, Conrad, Platyceras 

 Thetis, Hall, P. symmetricum, Hall, and P. carinatum, Hall. 



After making a detour around the falls it is at once apparent that 

 we are in a different formation, by the greenish color of the shales. 



We believe that all of the fossils found in this formation, the Lud- 

 lowville shale, are found in the higher beds, but the reverse is far 

 from being true. Brachiopods are quite scarce and there is a general 

 thinning out of representatives of all the orders. These shales are 

 succeeded by darker ones, thirty-five feet thick, containing nearly 

 the same fauna. These continue to the lower fall, which marks the 

 beginning of the dark, Marcellus shales, which continue to 

 Seneca lake. The only fossil which is here plentiful in the Marcellus 

 shales is Orthoceras subulatum, Hall. 



The thickness of these formations was obtained by taking a series 

 of levels from Bellona to Seneca lake. The results cannot be far from 

 correct, as the dip in that direction is scarcely appreciable. My 

 father, Dr. S. Hart Wright, a practical surveyor and engineer, assisted 

 me in the work, and the results may be relied upon as correct. 



Note. — The following description by Dr. J. S. Newberry, State Geologist of Ohio, ia 

 here published for the first time : 



Ctenacanthus Wrighti, n. sp. 

 Plate 16, figs.1-3. 



"Spine of large size, long-triangular in outline; anterior margin straight, laterally 

 " compressed ; medullary cavity large, opening posteriorly to the middle of the spine; above 

 " this point the posterior surface is traversed by a strong elevated rounded ridge; denticles 

 "small; directed backward; surface of exposed portion entirely covered with closely 

 "pectinated ridges of nearly uniform width on the front and sides, becoming narrower and 

 " less disinctly pectinated near the posterior margin. 



" The spines of this species must have been very striking in their characters, both as re- 

 " gards form and markings. The anterior margin seems to have been absolutely straight 

 "from base to summit. Along the line of junction between the enameled and buried por- 

 " tions the spine must have been two inches wide, but it tapered rapidly upward,terminating 

 "in a slender, acute point. The exposed surface is more completely covered with ridges 

 "similar in character, and the pectination is more crowded than in any other species known. 

 "In its broad base, its general and uniform ornamentation, this spine has some resemblance 

 "to C. speciosus, St. John, specimens of which have been in my hands; but the line of de- 

 " marcation between the ornamented and buried portions is less oblique, showing that the 

 "position was more erect; the ridges are considerably coarser and the form is straighter. 

 "The pectination is also less oblique and closer compared with the coarseness of the 



" Formation and locality.— Hamilton group, near the middle of the Moscow shal^Kash- 

 "ong creek, Yates county, New York, where it was obtained by Mr. Berlin H. Wright, 

 " from whom it is named." 



