22 



GEOLOGY hA SALLE COUNTY. 



The Trenton is eminently a fossiliferous rock:, 

 containing- the remains of many species of the animals 

 of that time, all marine, with some of algae or seaweed, 

 for land plants do not seem to have existed in that ag-e. 

 The animals are all w^hat we should call shell-fish or 

 moUusks — crustaceans, resembling- the crab and lobster 

 — celenterates or corals, and others of the lower forms 

 of life. The Covell creek locality has furnished several 

 species, as have the quarries west of Ottawa, but the 

 Troy Grove quarries were long- famous for the variety, 

 size and excellence of their specimens. These beds 

 are truly a "city of the dead." Here multitudes of 

 of the then lords of the sea, the giant orthoceros and 

 the yet more huge endoceros were entombed to be pre- 

 served for countless ages, and then brought forth from 

 their mausoleum to astonish and puzzle man. 



The following list is believed to give all the fos- 

 sils thus far known from the Trenton beds of La Salle 

 county: 



Blunienbachii, Calymene Troclionema umbilicata, 

 Raphistoma lenticularis, trilobite, Clark's Run, south- 

 west Lowell, Leer Park. 



From the Big Vermillion and Covell Creek we 

 have the following-: All cephalopods or resembling- the 

 nautilus of today Cyrtolites and Maclures coiled Otho- 

 ceros straight, the shell divided into chambers, the 

 animal living in the outer and larg-er one. 



Cyrtolites trentonensis, Orthoceras anellum; O. 

 junceum; O. vertebrale; O. titan; Cyrtoceros macrosto- 

 mum, Cyrtoceros constrictostriatum Maclurea; Conula- 

 ria trentonensis; and R.; near Lowell; Streptelasma 

 corniculum; Septena sericea, abundant; Orthis, Rhyn- 

 chonella, Strophomera, Buthotrephis suculens and B. 

 gracilis, Fucoids, abundant at Lowell and several other 

 species; also abundant two miles west of court house, 



