Notes on American: Geology. 247 
Remains of fish and their coprolites are occasionally found in 
the middle and upper portions of the transition, but the most dis- 
tinguishing feature in the paleontology of the system, are the 
trilobites in nearly all the strata; the vast proportion of Brachi- 
opods among the testacea, consisting chiefly of the genera Orthis, 
Detthyris, and Strophomena or. Lerrana, in the limestones; gi- 
gantic quadrangular fucoids in the sandstones, and small Linsias 
leaf-like fucoids in the slates. These latter first appeared in the 
lower slates, where other organic remains are very rare, but occa- 
sionally trilobites and shells of the genus Strophomena have been 
found, a fact. which induces-me to believe that these two orders 
were twin-born of the primeval seas, and that they were prece- 
ded by vegetable life. Mr. Phillips, in his investigation of the 
English equivalents, has been led to a different conclusion ; but 
England is a limited theatre for the display of the order of suc-— 
cession, which sinks into insignificance. in comparison with the 
colossal development of the transition in North America.. Mr.’ 
’ Phillips observes, “the classes of mollusca are more ancient than 
those of zoophyta, if we trust our present-knowledge, and both 
older than marine or land plants.”* We have, it is true, as yet 
no knowledge of zoophyta in the lower slates, and therefore the 
testacea may be more ancient than they, but marine plants are 
older than either. 
Among the brachiopodous bivalves, the genus Stuphomena of 
Rafinesque is the most characteristic of the trilobite system. Pro- 
ducta has as yet been found only in the upper term, or pyritifer- 
ous rocks of Eaton, where the species are very few and rare. In 
the mountain en above, Strophomena is hardly known, 
but it is crowded with Producta of many species. The latter 
genus, therefore, eminently characterizes thé carboniferous sys- 
tem, with which it ceased to exist. Not a single species of Te 
rebratula occurs in the Silurian system of this country, nor have. 
Iseen one from the carboniferous ; the shells hitherto classed in 
that genus being referrible to Orthis. 
_ Throughout. the transition, we very rarely find any ‘exidenoe 
of fresh-water streams or lakes; which is doubtless owing to the 
Very small proportion of dry land in those periods. The first 
trace of shew in New York is in the red sandstone at Medina, 
¥ 
* Treatise on Geology, p- 289. 
