536 PROF. T. R. JOTS^ES ON SOME DEVONIAN AND 



having a diagonal obliquity : it is more convex than P. humilis : 

 and its normal pit or umbilicus is large and without a furrow. 



From the decomposed Chert of the Corniferous Limestone (Devo- 

 nian), Ontario Co., New- York State. Collected by Mr. J. M. 

 Clarke, of Albany, N. Y. 



There are also in this rock some other more or less oblong, very 

 small casts of Primitice (?) ; and a few minute, almost oval casts, 

 indeterminable. 



Dr. Hinde, F.G.S., has favoured me with the following note 

 (March 27, 1890) : — '• The siliceous rock seems to have been com- 

 posed of calcareous organisms and then infiltrated with silica. 

 Subsequently the shells, &c., composed of carbonate of lime, have 

 been dissolved out, whilst the silica has been changed into ' rotten- 

 stone.' 



" I do not see any traces of siliceous organisms in the decayed rock ; 

 and, if these had been originally present, they have been dissolved. 

 I am very familiar with this kind of rock, which prevails in the 

 Corniferous Formation of Canada. Wherever it occurs, the corals 

 and other organisms are replaced by silica. I have often searched 

 for spicules in this chert before it has been decayed, but not with 

 much success, but I have some Indian arrow-heads made from it 

 in which spicules are plainly seen. 



" Dana, in ' Manual of Geol.' edit. 1875, p. 257, figures a variety of 

 microscopic forms* from this Corniferous chert or hornstone of 

 Central and Western New York, some Xanthidia, some perhaps 

 spicules, but the forms arc not very characteristic." 



II. Betrichia, M'Coy. 



2. Betrichia DEVomcAf, Jones. (PI. XX. figs. 1 a, Ih, 2a, 2h, 3.) 



Beyrichia, sp., Ferd. Eomer, N. Jahrb. f. Min. &c. 1863, p. 521, 

 pi. 5. figs. 9 a, 9 6. 



Beyrichia devonica, Jones, Geol. Mag. 1889, pp. 386-388, pi. 11. 

 figs. 3, 4, 5. 



Beyrichia (Bollia) ohliqua, Fr. von Sandberger, Jahrb. Nassauisch. 

 Ver. Heft 42, 1889, p. 33. 



Length 3*8 mm., probably longer than at first ; height 1*9 mm., 

 probably rather less than at first ; thickness about -9 mm., pro- 

 bably less than at first. 



Li the ' Xeues Jahrbuch fiir Mineralogie, &c.' Jahrgang 1863, 

 Heft 5, pp. 513-524, Prof. Dr. Ferdinand Homer gave a geological 

 account of a journey to Constantinople, &c., and included a notice 



* See also Dr. M. C. White, ' American Journ. Sci. & Arts,' ser. 2, vol. xxxiii. 

 1862, p. 386 ; and ' Geologist.' 1862, vol. v. pp. 239-240. 



t In the ' Neues Jahrb. f. Min.' &c. Jahrg. 1890, vol. i. p. 184, Dr. Frid. von 

 Sandberger mentions that B. devonica is identical with his MS. species Beyrichia 

 ohliqua, given in the list of fossils from the Lower-Devonian strata near 

 Offdillen, between Dill and Sieg, in the northern part of the Dillenburg 

 district, Nassau, as B. (Bollia) ohliqua, Jahrb. Nassauisch. Vereins f. Naturk., 

 Heft 42 (August 1889), p. 33 ; and he withdraws this latter name. 



