248 HA MITES. 



priately placed here, the characters of which, aside from the 

 mode of curvature, ally it to Hamites* the slight distortion of 

 the shell not justifying an independent genus. That an indepen- 

 dent genus cannot be established for these forms, is certain, and 

 doubt only exista a8 to whether they should IK- referred to 

 Hamites or Turrilites. a question which can only be definitely de- 

 cided when t he shells ;ire more accurately and completely known. 



With the change in the spiral, a change often takes place in 

 the sculpt ure. which is often distinctly strengthened; this is 

 however, not the case with the commencement of the series of 

 forms, but occurs somewhat later, some time after the separation 

 from the involute ancestral form. 



A. character which appears with remarkable constancy in the 

 involute Lijtoceratidse is gradually lost in their evolute sin-. 

 Ors, namely, the two-pointed ending of the antisiphonal lobe. 

 In some of these this part is retained, as is shown in part 

 by existing figures, and partly as I have learned from a study of 

 the Pictet Collection, this is the case in Crioceras depress m, 

 Ancyloceras alternatum, saussureanum, pseudoelegans, Hamites 

 boucfiardiamus, alter no-tuber culatus, elegans. In many others. 

 however, a one-pointed structure steps in, and I conhl convince 

 myself that this occurred by one point uniting with the other : 

 it is very apparent in forms which are. derived from the spiral 

 in one plane that a distortion takes place, although a one-pointed 

 antisiphonal appears also in forms in which the spiral is in one 

 plane, even though from the minuteness of this character I could 

 Hot unqualifiedly admit this in respect to all the species which 

 arc figured in this manner. 



l-'or the forms here named one genus is quite sullicient. and 

 we choose, for evident reasons, the oldest name. Iltimitux. 'Rela- 

 tive to the other cret accous Ammonites, compare below on 

 Tiirrililrx. Jlm-iil ih-n^ SVflr/////7rx and Crinrvras. 



In the lowest cretaceous strata (IJerrias) we find no //fiinif''*. 

 and in general no evolute Ammonite : theoldi-st representative 

 may be considere<l to be //. }'ratiii, from the appearance of which 

 the genus extends through the whole cretaceous; they si-em to 

 reach their maximum of development in the gault. 



H<nnit>.< i> certainly not a monophylet jc genus; whilst the 

 majority of the form- -land in closest relationship to Hamites 



