THE DEVELOPMENT OF SCAPHITES 653 



connection. If retardation be assumed to take place, it is clear that 

 it will be noted first in the case of the lobes and saddles nearest the 

 ventral lobe, for these are the oldest. In this figure the first auxiliary 

 lobe is seen to develop normally into a triaenidian lobe, while the 

 first lateral develops in a dicranidian lobe. In time it is quite possible 

 that through unequal acceleration all the lobes will become dicranidian. 



VARIATION 



In all the varieties and species of Scaphites studied the variation is 

 seen to be very pronounced. In the variety brevis we find nodes 

 away down in the young stages long before they appear in similar 

 stages of plenus and quadrangular is. In the Oregon and California 

 species we do not find them until the very last. In the ribs, too, 

 there is seen to be a great diversity. We evidently have to deal with 

 modifications, some of which have been acquired and pushed back 

 in the ontogeny to earlier stages, and others that have been lately 

 assumed. If we could find the progeny of some of these varieties, 

 we might be able to see differences enough to warrant calling them 

 species ; for varieties, if given time enough, will undoubtedly produce 

 species. 



CONCLUSION 



We are of the opinion, then, from this study, that the genus Sca- 

 phites is in need of revision; that a number of "morphological 

 equivalents," to use Hyatt's expression, have been grouped together 

 as species of one genus; that this genus is polyphyletic, and not 

 monophyletic, as it has been treated heretofore; that both groups of 

 Scaphites are degenerate, phylogerontic forms; that the nodosus 

 group, from Montana, sprang from some member of the Sephano- 

 ceratidce, while the Oregon species probably originated from the 

 Lytoceratidce, or the ancestor of this group. 



In the nodosus group we have a number of varieties that are on 

 the road to becoming species. In the two so-called species from 

 Oregon and California it is our opinion that we have varieties merely. 



Scaphites perrini, found with S: inermis and cononi by Mr. 

 Anderson, may have come, not from the Lytoceratidce, but from 

 Stephanoceratidce. This is based on the aspect of the whorl, the 

 young stages not being available for study. 



