Report of the State Geologist. 171 



Centronella, Billings, 1859. 

 Cryptonella, Hall, 1861 . 

 Scaphiocoelia, Whitfield, 1890. 

 Hallina, Winchell and Schuchert, 1892. 

 Rensselaeria, Hall, 1859. 

 Megalanteris, Suess, 1856. 

 Notothyris, Waagen, 1883. 



Eichwaldia, Billings, 1858. 

 Aulachorhynchus, Dittmar, 1872. 

 Richthofenia, Kayser, 1883. 

 Lyttonia, Waagen, 1883. 

 Oldhamina, Waagen, 1883. 

 Almadenia, Pohlig, 1892. 



Plates. During the years from 1871 to 1881 eleven plates of 

 Spirifers were lithographed and the entire edition printed in 

 preparation for this work. During the progress of the work on 

 volume yill, part 1, 1889, five additional plates of this group of 

 fossils were lithographed and printed. Besides these we have 

 now twenty-four plates drawn on stone, some of which have been 

 proved, but none are as yet printed. These together make a 

 total of forty plates which may be regarded as finished for the 

 second part of the volume. For the proper illustration of the 

 work about twenty-five more plates will be required, the draw- 

 ings for which may now be considered as essentially completed. 



Geological Map of the State. 



A geological map of any country or portion of country is of 

 the first importance to its inhabitants. The limits of rock 

 formations where they contain valuable minerals or otherwise 

 is of importance, and in fact there is no rock formation of any 

 considerable extent but has its economic importance in every 

 country which mav come under the domination of civilized man. 

 At the outset there is an effort made to learn the limits and 

 distributions of the rock formations and their mineral contents. 

 Early geological maps of any country are necessarily crude. 

 The accuracy of the geological representation must depend upon 

 the degree of perfection of the geographical or topographical 

 maps which may be used as the base for illustrating the geology. 

 We therefore find that not only the geological maps but also 

 all geographical maps of any country, are, in their inception and 

 early stages crude and incorrect, giving only its larger rivers and 

 higher mountains which are the main features of the country, 

 but much is represented from incomplete exploration or given by 

 inference or imagination. As an illustration of this condition our 

 people are at this moment gathering together all the old maps 

 which can be found in any part of the civilized world relating to 



