PREFACE. 15 



fore species were often based upon superficial, trivial charac- 

 ters, which are relatively unimportant as classificatory criteria. 



In considerations involving problems of synonymy, which 

 have arisen prominently during- the progress of the work, every 

 effort has been made to pass unbiased judgment in accordance 

 with the merits of each individual case; and when any dis- 

 crepancies have occurred, the respective aathors have been 

 given every benefit of the doubt. Through the kindness of 

 the various owners, hereafter mentioned, a large number of 

 type specimens were critically examined. Many questions of 

 identity, previously doubtful, were thus satisfactorily settled. 

 To be sure, in some instances the same test may appear seem- 

 ingly to have decided similar questions in very different ways ; 

 but there have always arisen minor points in the one or the 

 other which do not strike one forcibly at first, though when 

 once attention is called to them, they can readily be seen to 

 have an important bearing in attempting to do full justice. 



Considerable surprise has been expressed at various times 

 during the progress of the present work, especially by those 

 somewhat interested in geology residing in the State, at the 

 lack of effort made to describe new species. The reasons for 

 this seeming inappreciation of " new " species are numerous. 

 In the first place, the main-spring of action in the description 

 of the large majority of the species now known has not been a 

 keen desire to advance our knowledge on the subject, but 

 rather to merely attach one's name to as many specific terms 

 as possible. The great number of forms indifferently described 

 from fragmentary material or without illustration of any kind, 

 and the host of undoubted synonyms, only too fully corroborate 

 this statement. Paper after paper has appeared, made up en- 

 tirely of mere incomplete diagnoses of " new species." If 

 some of them had been accompanied by even slight references 

 to the morphological and geological relations, there might be 

 a demand for this class of work. But such has not been the 

 case in fully one-half of all the forms that have been named 

 from North America. Many specimens have been so imperfect 

 that even the family affinities, to say nothing of the generic 



