650 



W. D. SMITH 



.73 mm , §• revolution, there is a constriction which is quite as marked, 

 when seen, as in the young Baculites and Lytoceras. The presence 

 of pustules could be detected only faintly, not nearly as well marked as 

 in Scaphites nodosus. The first lateral saddle is notched at a diameter 

 of 3-4 mm , or 3! revolutions. At this stage the lobe is bifid, and not 

 trifid, just as in the nodosus group, with this difference, that the forms 

 of the nodosus group are more accelerated in this respect. There is 

 very little change in either of these species in the adolescent and 

 early ephebic stages, not as much as there is between Meek's varieties 

 of nodosus. 



It does not appear to the writer, after a study of these forms, that 

 Mr. Anderson found enough differences to warrant him in calling 

 them distinct species. It seems that they differ only in late ephebic 

 stages, and then in a little minor sculpturing. The two are flat, 

 rather thin, with no sculpture until the last coil. It is probable, 

 however, that if these forms had given rise to any progeny, the descend- 

 ants would have shown that these slight differences had been pushed 

 back and added to until there would be no mistaking even the young. 



As these forms were all preserved as casts, the shell itself could 

 not be studied. Whether there was anything distinctive about it or 

 not, resembling any other group, of course remains to be settled. 



For comparison the following table has been drawn up: 



TABLE II 



Scaphites inermis And. 



Diameter of shell . . . 

 Height of whorl. . . . 



Width of whorl 



Involution 



Width of umbilicus. 





II III 



o. 16 o. 20 o. 28 

 o. 16 0.04 0.08 

 0.4910.48 0.48 

 Too small- to measure 



. . . . I . . . I0.36I . . . . I0.64 



IV 



0.52 

 0.24 

 0.49 



0.76 

 0.24 



0.52 



VI 



1.24 



0.48 



0.56 

 0.6 



VII 



1.76 

 0.52 



o. 72 

 o. 14 

 1 .24 



VIII 



2.52 



0.76 



1.08 



IX 



3-5 2 

 1 .00 



1 .60 

 0.48 

 2.50 



mm 



5-72 

 2. 20 

 2.4O 

 0.20 



XI 



Ppylogeny. — From a study of the young stages of Baculites and 

 Lytoceras, both from the material itself and J. P. Smith's 1 papers, 



1 J. P. Smith, "Larval Coil of Baculites," American Naturalist, Vol. XXXV, 

 No. 409; "Development of Lytoceras and Phylloceras," Proceedings oj the California 

 Academy 0} Science, 3d series, Vol. I, No. 4. 



