HISTORICAL SKETCH. xlvii 
The second paper compares, bed for bed, the different parts of the Lower Silurian in 
Minnesota with their supposed equivalents in Wisconsin, and divides the same in Minne- 
sota as follows, naming some of the characteristic fossils of each. 
The Cincinnati group comprises: 
Wiykoitabedsolimes tones sack <tes-cle ne cincie te nicerareicie raver = 50 feet 
Maquoketa beds, limestone and shale.................... A) Ge 
The Galena embraces: 
Machunearbedrrlime@stOmeercrscicisisreo citi o savers a a/elete atetekereveyeteie 50. 
inoulasmaybeds limteston eres sctclew sitacisiccierae te ee ees 20 
Camarellajbeds limes Comet ercrnjaey-1aletciers oo epaiotore = eke ore citi 30“ 
Orthisinajbed \shaley ver ccriaycciieteciei coerssensicreisisionsts ereciclers 20s 
In the Trenton are placed the following: 
ZV SOSpiraWeds ShalOkts srevartee seit ats!srsierole tis ays ieraveuselels eerie. arate Siac 
Hucold bed wshial Cpmerkeewtriyetrterclslerseeiertere a eelevoseiee ais aig) Ge 
Stictoporasoeus sliall Ohetecar:aiyac sys. /recrsresieyieereree chen ioe EXO) es 
wlictoporella bed) shalelie< = yo. ssc -cinele cs seis): etic LOR 
Blues bed mlimestonee cece cisietowi sisi tic aisnerore te oouerebeeiererare Themes 
Bui bed Slimestones Ses cctschsicsiey, bate texas os, <ielae coe aia eee 15 
MMO tall re soece Reertcsses ey stat cosa oie eels set 618) ela cucreiatene oares 285 
This substantially divides the strata covered by the investigations of this volume into 
three limestones separated by two epochs of shale. The Devonian is said to lie uncon- 
formably on the Wykoff limestone. 
The third paper describes a number of new forms and presents a table showing the 
stratigraphic range of all the species found by the author in the Lower Silurian; the same 
subdivisions are used as above. These three papers constitute an important addition to 
the stratigraphic paleontology of the Minnesota Lower Silurian. 
C. W. Hall and F. W. Sardeson. 
1892. Paleozoic formations of southeastern Minnesota, by C. W. HALL and FEF. W. SarR- 
DESON. Bulletin of the Geological Society of America, vol. 111, pp. 331-368, June 28, 1892, 
This paper repeats the classification and the paleontological results expressed in the 
foregoing papers of Mr. Sardeson. It embraces also varicus structural and petrographical 
information relating to the Upper Cambrian and the Lower Silurian in Minnesota. 
In speaking of the paleontological characters of the St. Peter sandstone some fossils 
lately found near St. Paul are named, which in the opinion of the authors show the Lower 
Silurian age of thissandstone. They are: 
Murchisonia gracilis Hall. 
Murchisonia perangulata Hall. 
Two new species of Modiolopsis. 
Undetermined species of Tellinomya. 
Undetermined species of Endoceras. 
THE REPORTS OF THE MINNESOTA SURVEY. 
1872-1892. Several of the annual reports of the Minnesota survey have dealt with 
the strata and the fossils of the Lower Silurian, viz: 
