1 PREFATORY NOTE. 



into the nature of the species described as Tentaculites. On pages 162-165, 

 vol. v, pt. ii, some discussion of this subject has been introduced, and for the 

 purpose of farther elucidation material from various sources was procured for 

 the illustration of the Lower Silurian forms heretofore referred to the genus 

 Tentaculites, and to the more recent genera Conchicolites and Ortonia, pro- 

 posed by Prof. Nicholson ; there being already in hand, from the Waldron col- 

 lections, sufficient material for illustration of the principal phases presented in 

 the development of the Niagara species. 



The acquisition of new material among the Pteropoda, made it desirable to 

 give some farther illustration of this class, and especially of the Tentaculites, 

 for a better means of comparison with described forms, and also to show their 

 distinction from the elongate annulated forms of Cornulites usually referred 

 to the former genus. 



I have, therefore, introduced in this connection, and following the illustra- 

 tion of Tentaculites and other Pteropoda, Plates cxv, cxvi, and cxvi a, for the 

 purpose of showing the varying phases of development among certain forms 

 belonging to the genus Cornulites. These plates were introduced primarily, 

 for the purpose of affording means of comparison with authentic forms of 

 Tentaculites since some of the species of the former genus, in their free con- 

 dition, so closely resemble the latter that they have been mistaken for the same 

 and described as Tentaculites. 



The plates cxvii to cxxix inclusive are given to the Cephalopoda, of which 

 twenty species here described are not illustrated in Vol. V, part ii ; together 

 with a number of others already there described and figured, but which are 

 important as presenting additional features to those already illustrated. All 

 these plates have appeared as photo-lithographs, accompanied by explanations, 

 in tlie Fifth Report of the State Geologist (1886). 



THE AUTHOR. 



March, 1888. 



