NOTES ON THE POSITION OF THE INDIVIDUALS 
IN A GROUP OF NILE US VIGILANS FOUND 
AT ELGIN, IOWA. 
BY G. E. FINCH. 
David Dale Owen made note more than fifty years ago 
of the multitudes of fragmentary specimens of Asaphus 
iowensis in an exposure at the junction of Otter creek with 
the Turkey river at Elgin, Iowa. From then on, that 
locality has been classic trilobite territory. The most 
abundant species to be found entire there now, if good 
trilobites can be said to be abundant anywhere, is Nileus 
vigilans, which occurs both enrolled and more or less 
straightened in form. Everyone who has collected this 
species knows it to be gregarious. The collector may look 
for hours without finding a single specimen, then pick up 
two or three nice ones in as many minutes. In the sum- 
mer of 1908 it was my fortune to find in situ on a small 
rock two or three feet in length by one foot in width, some- 
fifteen entire specimens. The place is a rocky run, a mile 
below Elgin, on the north side of Turkeyfriver; and the 
horizon is in the Maquoketa shales about forty feet above 
the base. The stratum in which they were imbedded is of 
limestone, about two or three inches in thickness and 
without apparent lamination. Overlying it is a thin, 
argillaceous, laminated layer separating it from another 
limestone layer above. 
The trilobites found there were all entire ones and 
belonged to the same species, N ileus vigilans , the Asaphus 
vigilans of Meek and Worthen* Some were nearly rolled 
*Minn. Geol. Surv. Vol. Ill, pt. II, page 712, and Geol. Sury. Ills., Vol, II, page 497, 
and pi. 23, fig. 6. 
079) 
