CRAB EH VELL 
Tiree O Wik: Shiv RAN: PRILOBEFES 
| OF MINNESOTA. 
BY JOHN M. CLARKE. 
INTRODUCTION. 
The trilobites have long invited the attention of observers, the curiosity of the 
novice, and the most intelligent scrutiny of the student. Much of this interest lies 
in the frequent beauty of their preservation, their abundance, their complication of 
structure, and, no doubt, largely in the fact that the organic plan upon which they 
are constructed is long since extinct or only obscurely recognizable among their 
living descendants. It has been for the paleontologist to elucidate not only the 
various modifications of this plan of structure, but to demonstrate the anatomy both 
of their hard and soft parts, their alterations of form in the process of development 
from infancy to old age, the rise, progress and decline through time of subsidiary 
structural types. For this work science acknowledges its obligation to the pioneer 
investigations of Dalman, Brongniart, DeKay, Green, Pander, Emmrich and 
Burmeister; to those of McCoy, Salter and Woodward upon the species of Great 
Britain; of Beyrich, Corda, Barrande, Kayser, Novak upon those of Germany and 
Bohemia; of de Verneuil, Rouault, Barrois, Ehlert, Bergeron upon those of France; 
of Meneghini upon the Sicilian species; of Pander, Nieszkowski, Kichwald, Schmidt 
on the Russian species; Angelin, Holm in Scandinavia, and Hall, Ford, Walcott, 
Matthew and Beecher in North America; a list to which many names might be added. 
The Trilobites have proved of first importance to the stratigraphical geologist 
as indices of geological age, and every new series of investigations emphasizes the 
importance of their various modifications to the student who busies himself 
primarily with the structure of the earth and the correlation of the early sedimen- 
tary deposits. To the names above given we should append those of investigators 
who have apprehended the trilobites mainly from this point of view; Conrad, 
Emmons, Murchison, F. and A. Roemer, Linnarsson, Dames, Billings, Whitfield. 
[695] : 
