Base of the T((co)>ic or Lotrer Camhrid ik — WuK-hell. 221) 
.'!. 151iick thinly laminated clay. 
Fig. 1. Section (if Lower Claiborne (4 miles soiilli of tiibbsland uii 
the La. A: X. W. railway. Lcnjrth of cutlinj;- olO feel: depth. IGi fpt-l. 
1. lU'd clay, with some sand in the upper portion, passing into 
'I. (Jray laminated clay ("Arcadia clays"), passiiii: into 
o. lilack Ihiidy laminated clay. 
F'k;. o. Section of lower Claiborne one-half mile north of Natchi- 
toches on Old river. No. 1 is a yellow calcareous marl with calcareous 
nodules, formini.:' a prairie soil. Oxfira .■<r//ii'f(in)iix -.lud -.iw (irfjifuHnd-likf 
foraminifer are very abundant in many places on the surface. Helow 
the surface a few feet, sometimes fossils are numerous, sometimes only 
calcareous nodules are present. 
, Helow the liirnite seam (:>), the laminated sands and clays sometimes 
.show cross-lieddinu'. 
Fig. (■). S<'clion of l)lutf on Saline bayou one-half mile aho\-e St. 
Maurice, showing fossiliferous L(jwer Claib<irne (4). o\erlaid by the 
<V)cksfiel(l Ferry beds (2). I do not know whetlier)! should be referred 
to the same caletiory as 4. or classed with '1. 'Vhf whole section, ex- 
cepting L is one conformable series. No. 1 is gravel. prol)ably of Co- 
lumbia age. 
Fig. 7. Seciion at Cocksfield Ferry, showing- the (dcksHeld Ferry 
beds, lou-er pari of section une.\posed. No. 1 is i:ra\e|. ])robably of 
Columbia aue. 
Fig. S. Section near the up[ier end of the l)lulf at Montgomery 
.showing the .lackson '*. ."!. and 4o\erl\inir the Cocksfield Ferry beds (» 
and 7. 
Fk4.9. Section one-half mile west of Provencal on the T. v\: 1*. railway, 
.sliowing what is jjrobably the basal contact of the Sparta sands. Cul- 
Jiiig 240 feet long, !> feet deei), 
L Yellowish sand witii some clays, resting unconformably on 
2. Stratified red clay with wliite clay part iiigs. mantled by soil. 2', 
probal)ly Eocene. 
3. Hjematilic iron ore de\cloped along the contact of 1 and 2. 
[CRuri.\i. POINTS IN THE c;eoloc;y of the L.\ke Sli'Erior reoion. No. 2.] 
THE PALEONTOLOGIC BASE OF THE TACONIC OR 
LOWER CAMBRIAN. 
I5y X. II. WiNClll-.l.L. .Miinieapiilis, Minn. 
It was (irst in America that an etloft was made to define 
the base of tlie Cambrian by fatmal chitraetcrs. From time to 
time lower and lower portions of tiie Ciunbrian strata were 
found to contain a characteristic trilobitic fiinna. in Kiirope, 
and especially in Scandinavia, and without iu-sitation sticii 
strata were tidmitted into the Cambrian system. Harratnle's 
