( 'ovvenpondence. 1 33 
p'rth: Resume of the stratigraphy of eastern Kansas, E. Haworth; The 
topography of eastern Kansas. E. Haworth; Surface gravels in eastern 
Kansas. I']. Haworth). A geological reconnoissance in southwestern 
Kansas and No Man's Land, E. C. Case; Traces of a glacier al Kansas 
City, Mo.. E. ('. Case: New genera and species of Dolichopodida?, .1. M. 
Aldrich: Descriptions of North American Trypetidae, with notes, Pari 
1. W. A. Snow. 
The School of Mines Quarterly, vol. 1">. no. 2, .Ian.. 1894, contains: 
Acanthite from Colorado, A. H.Chester; In<le\ to mineralogical litera- 
ture, A.. I. Moses and L. Mel. Luquer. 
Johns Hopkins University Circulars, vol. \'-'>. X<>. 112, May, 1894', con- 
tains: On the attractions of crystalline and isotropic masses al small 
distances (abstract). A. S. Mackenzie; Notes on crystals of scapolite, 
gypsum and fayalite recently acquired by the University cabinet. (<.(). 
Smith; Note on an apatite crystal From Alexander county, X.C. L.M. 
Prindle. 
CORRESPONDENCE. 
Trilobites in the "Oil-Rock" Horizon of the Trenton Limestone. 
The Upper Blue limestone member of the Trenton group in the lead re- 
gion of Wisconsin is generally highly fossiliferous. There are, however, 
considerable local differences in the grouping of genera and species, and 
especially as to quantity and condition of preservation. Al one of the 
mini's of lead ami zinc ore of the Wisconsin Lead and Zinc Company in 
the township of Shullsburg, Lafayette county, I have recently found 
several species of trilobites in a remarkably good state of preservation, 
and showing details of structure not usually seen. Thus, aside From the 
interest attaching to the discover}' of so main of these organisms in 
close association with lead and zinc oris, the locality promises in afford 
valuable material to the specialists who are now invest iga bing the struc- 
ture of trilobites, and who have of late so greatly extended our knowl- 
edge of it . 
The genus Ceraurux is the mosl frequently represented. In most of 
the specimens the shell remains in the rock, but in an extremely soft 
and Fragile condition, white and chalk-like, much resembling egg shell, 
hut not so hard or tough.* Bui all the minute details of the shell are 
well preserved and maj be seen not onlj upon the shell, when it can he 
saved, but upon the casts in the rock, both above and below. It is not 
possible to obtain complete individuals, but in breaking up the rocks 
where many of the fossils are grouped together some Fragments exhibit 
one portion and some another, so there is little difficult} in making out 
t he ent ire st rue! ure. 
The cephalic portion of Cerauru* is the most abundant. There up 
♦Fragments are rapidly dissolved with el »\ tiydrochlorii acid. 
