288 
THE GEOLOGIST. 
Mr. Sharpc, becansc it liavmonizes very well wtli my Aacws on the 
subject. 
I, North America. — FoUdam Sandstone. 
Professor Hall only cites two Lingulse and the Scoh'thus linearis 
here. Professor Rogers is said to have found a Discina. Sir C. Lyell 
speaks of something resembling a Placnna. The profiles given by 
D. D. Owen (see Rep. on Wisconsin, Iowa, &c., p. 499, &c.), cite 
Lingula and Discina in the deepest beds, and the first other genus 
appearing is Orthis. 
The C'alciferuus sandstone does not show any marked difference in 
the character of Brachiopoda. Vanuxem and Hall only speak of a 
Lingula found in a loose block. Bigsby mentions L. ohtusa aud 
Ortliidcs here. 
The Chazy limestone, on the contrary, contains ten species of Bra- 
chiopoda (according to Hall), one single doubtful one, Orhicida (?) 
defonnis, belonging to the shallow water gi'oup A, the rest having 
opaque shells, and only embracing one single Orthis. 
The Binlseye limestone contains no Brachiopoda, according to Hall. 
The statements of Dr. Bigsby seem to be somewhat contradictory 
(Quart. Jour., 1858, p. 431 and lists.) 
The Trenton limestone seems to form a great exception, and to con- 
tradict all these statements in containing at the same time a great 
number of species both of group A and of group B. Still, in 
gathering the facts relative to the recvirrence of these species in the 
overlying strata, it may be shown that no contradiction exists. In 
comparing the lists of Brachiopoda fi'om the Trenton limestone, Utica 
slate, and Hudson river group, as I intend to do now, it is, I fear, 
necessaiy to omit those given in Dr. Bigsby's lists with the authority 
of Sliarpe, because Sharpe united these three strata iinder the 
denomination of blue limestone of Ohio, and the species named by him 
in this bed are cited witli his authority as B in eveiy one of the 
three strata. The following species are said to rise from the Trenton 
limestone into the Utica State, and as no new species of Brachiopoda 
appears in the State, they form the whole of the species found in it* : — 
Spiri(jerina reticularis, Uliynchonolla increbescens, R. modesta, R. hiden- 
tata, Strophomena alternata, Orthis lynx, 0. testudinaria, lAngula 
ohtusa, L. curta, L. ovata, L. quadrata. The proportion is much more 
in favour of group A here than in the Trenton limestone. In com- 
paring the Hudson river group, you will find in it : — 
a, Species found in Trenton limestone, but not in Utica State : 
Lingtda crassa, Orthis Tidliensis. 
h. Species passing indifferently through all three strata : Spiri- 
gerina reticularis, llhynch. increbescens, li. modesta, R. bidentata, 
Btroph. alternata, Orthis lynx (?), 0. testudinaria. 
* Mr. Hall's list cites Lex>t. sericca hero foi' tbo first time. 
