PRELIMINARY PALEONTOLOGICAL REPORT, 



CONSISTING OF 



LISTS Ai\D DESCRIPTIONS OF FOSSILS, 



WITH REMARKS OX THE 



AGES OF THE ROCKS IN WHICH THEY WERE FOUND, ETC., ETC. 



B5^ F. B. MEEK, Paleontologist. 



GEl!fERAL EEMAEKS. 



SILURIAN AGE. 



East side Gallatin Bivet\ &c. — AU of tbe Silurian fossils collected by 

 the survey, during tbe explorations of 1872, evidently came from compara- 

 tively near the base of the system. The specimens from the east side 

 of Gallatin Eiver, above Gallatin City, Montana, were collected from 

 four subdivisions. Those from the lowest or fourth subdivision, (num- 

 bering from above,) are few, and in a fragmentary condition. Among 

 them we have one of those curious bodies formerh^ sometimes called 

 bilobites, ai:>parently under the erroneous supposition that they have some 

 relations to the Crustacea known as trilobites, though they are now gener- 

 ally regarded as marine plants, and designated by the generic name Cruz- 

 iana, d'Orbigny, (Eusophycus, Hall.) Along with this fossil were found 

 imperfect specimens of Lingula, or Lingule2ns, Co7iocoryp]ie, Bathyurus, 

 &c., which, when taken together, point to a rather low position in the 

 series, especially in view of the forms that occur in the succeeding sub- 

 divisions above. 



From the third and second subdivisions, occurring successively above, 

 we have the genera Acrotreta, IlyolitJies, Agnostus, ConocorypJie, Bathy- 

 iirus, &c., a group of types which, in the present state of paleontological 

 science, could hardly be expected to occur together, higher in the series 

 than the Quebec group of the Canadian survey. And, when we take 

 into consideration the entire absence among these collections of any 

 type elsewhere peculiar to any higher horizon, and the fact that several 

 of the species are closely allied to forms found in rocks of that age, we 

 feel quite safe in referring these beds to the Potsdam, or Primordial 

 zone. 



Big Horn Mountain. — The same may probably be said of the rocks 

 from which a few fragments of Conocoryphe and DiJcelocephalus were 

 collected on the west face of Big Horn Mountain. 



The few specimens from the lirst or upper of the subdivisions at the 

 locality referred to above Gallatin City, are in a fragmentary condition, 

 but from the position of this subdivision above the others, as well as 



