THE DEVELOPMENT OF SCAPHITES 637 



Desmoceras hoffmani Placenticeras pacificism 



Desmoceras sugatum Schcenbachia oregoncnsis 



Desmoceras ashlandicum Arethusa call) arnica 



Baculites chicoensis Nautilus sp. ( ?) 



Helicoceras breweri Scaphites inermis 



Helicoceras declive Scaphites condoni 



Ancyloceras lineaium Scaphites gillesi 



Lytoceras sacya Scaphites perrini 



Lytoceras jackonense Scaphites roguensis 



Lytoceras jukesi Scaphites klamathensis 



The first two in the list of Scaphites, S. inermis and S. condoni, 

 have been selected for study principally for the reason that there was 

 more material of these two species available for the work. 



In connection with these the following have been studied: 



Sonneratia stantoni 



Desmoceras beiidanti 



Desmoceras hoffmani 



Lytoceras alamedense \ , . _ , , , T _. _, ... . 



„ ,. , . . ) chiefly from the papers by J. Jr. Smith. 1 



Baculites chicoensis J 



P achy discus 



All drawings have been made with the camera lucicla, either with 

 or without the microscope. 



The very young stages have in most cases been enlarged thirty 

 diameters, and some of the larger adolescent stages only ten, while 

 the adults are represented at natural size. 



The writer wishes to express his appreciation of the valuable aid, 

 in the matter of suggestions and in furnishing some excellent material 

 to work on, rendered by Professor J. P. Smith. Acknowledgments 

 are also due Professor Stuart Weller for valuable assistance and 

 opportunity extended to the writer to examine material from the 

 Upper Cretaceous of New Jersey. 



DESCRIPTION OF SPECIES 



The writer does not feel called upon to add to or repeat the descrip- 

 tion of these forms as found in Meek's or Anderson's works, more 

 than to state just enough to aid the reader and save him the trouble 

 of referring to these larger works. 



1 J. P. Smith, "Development of Pytoceras and Phylloceras," Proceedings of the 

 California Academy of Sciences, 3d series, Vol. I, No. 4; "Larval Coil of Baculites," 

 American 'Naturalist, Vol. XXXV (1901), No. 409. 



