PREFACE 



CEVERAL years ago we commenced a series of papers in "Bulletins of American 

 Paleontology," dealing with the molluscan remains in the various horizons of 

 our southern Tertiaries. In these the subject matter is treated stratigraphically ; in other 

 words, the Midway stage was first taken up, then the Lignitic, and now the Claiborne 

 is in press. Other papers dealing with special localities or horizons have also been pub- 

 lished. In future numbers we hope to discuss all important Tertiary horizons strati- 

 graphically. This seems the natural way for all investigation of this preliminary na- 

 ture. Witness for example Hall's works on the paleontology of New York as well as 

 the paleontologic matter included in our various state survey reports. Such papers if 

 printed in small octavo form are convenient for field use as well as laboratory study. 



But as years pass by and the faunas of the various horizons are better understood, 

 and vast amounts of material collect in our museums, there comes a time when a purely 

 biologic phase of investigation may be advantageously undertaken. Note for example 

 the more recent works of Clarke and Ruedemann of the New York survey. This calls 

 for a larger sized publication, admitting plates of sufficient dimensions to contain for 

 comparison representatives of many closely allied types of life. And, the larger size 

 page will be found not inconvenient in laboratory and museum where desks and tables 

 are at hand; in the field, a work arranged biologically would scarcely ever be called for. 

 Accordingly, this new work has been begam to receive such papers on invertebrate pale- 

 ontology as are arranged systematically, papers that will be of direct assistance to stu- 

 dents of biologic evolution. 



The first of these papers, unpretentious and seemingly easy of preparation, has cost 

 the author a vast amount of study here and elsewhere to make sure that no serious 

 omissions of specific or varietal forms have been made either in the text or plates, and 

 that the figures and text indicate clearly the characteristic features of each form disaissed. 



Pnleontological Laboratory 



Cornell University G. D. H.vrkls 



October ,30, iqt6 



