.'{2 77/C A llic/rlcji II CcohxjiHf. January. 1S97 
should })o easily rocofjnizahlo to the ^eolofjisl as not Gak-na fTrenton; 
for even in the well knfiwn triloV)ite bed at Elgin, Iowa, wliere the fos- 
sils are a few species only, one finds Or<///.s kankdlceriHis McChes., O. 
ciiKicerdlii. H.,0. biHc/nlpta H. and others that are no other than Ma- 
quoketa (Hudson) fossils. But in this bed as in the Diplor^ray^tus bed, 
OrihiH siihqiinflnita H. and SfropJionunui, frilohaid Owen (S. flexuosa 
Bill.) and perhaps for that reason it has been mistaken for " IVenton." 
13. LEPTyKNA RED. 
The succei^sion of small ex-posures that are found ahjng the railway 
west of Wykoff, Minn., represent about 30 feet of fine-grained, soft 
limestone that there compo.ses this bed. In some .strata fossils are very 
numerous, often silicified. but are not accompanied by quartz concre- 
tions. Near the Iowa and Minnesota boundary, Vjy Granger and Flor- 
enceville, it is found with the next lower bed often in one contiguous 
exposure. It is distinguished from the Orthoceras bed by the manner 
of weathering into slabs instead of into blocks, and likewi.se by afaucal 
change. Near Postville, west of Elgin and near Eldorado, Iowa, it is 
to be seen and is fully 75 feet thick, consisting of limestone at the 
top and of lime and clay or chiefly clay in the middle or lower portions. 
At the base there is a sudden transition to the purer limestone of the 
Orthoceras bed. 
Farther south it has not been oV>.served, except that there is a great 
bed of unfos.'^iliferous, impure clay, evidently extant in its supposed po- 
sition at Graf. Iowa. East of Scales Mound, Illinois, a very imjjure 
limestone, seen 20 feet, is probably the same, but there were found two 
species of triiobites (Asaphus) only and they are common to all beds of 
the Maquoketa series, hence it is not certain that the strata in question 
do not belong to the Orthoceras bed. At Graf, Iowa, and northward 
no fossils were found until reaching Elgin, but thence northward to 
where the bed is entirely removed in southern Minnesota fossils are 
more abundant, some strata near the top Vjeing full of them. 
Ortlih subqitadrata H., Plectanihonitea recedens iSar.) and Rhyncho- 
nella pei'hnncllosa Whitf., are very abundant in the limestone: the first 
is known only from this and the Triplecia bed (10), the other two in this 
and the succeeding bed only. Species of Lej^tazna are most aVjundant. 
An interesting fauna is found at Wilmington, Illinois, in shales close 
Vjelow the Niagara limestone, and it is evidently the equivalent of this 
bed, or po.ssibly of the next one. 
14. Orthis bki). 
Upon the Lept^na bed at Spring Valley. Minn., near the type expo- 
sures of that limestone, there is found in many exj»osures a bed of 
mixed lime, clay and quartz sand in different proportions in different 
strata. The bed in this locality is subject to flooding by water that 
pours out of the crevices in rainy seasons, so that one can not rely upon 
the condition of the strata as positively primitive, but some sandstone 
strata with fine mud-covered upper faces that are here found are possi- 
bly proof of a litoral deposit. There are very few fossils, and in the 
