II AMI I I 



the establishment of a superabundance of <Tnl 



trial I believe lh:it the following may In- included in ll:nnil< 



1'xn-iil I,KI. lln iinilniit. llt-l. 



yv//7/ff/v/>-. '/' roceras. 



The principal reason why I MIII iieee>sil;it .-d to -uppre>- ti 

 genera, is this: Hint in their charaHeri/at ion. only the ehi 

 ters pre\aleiit in the sperics of the series belonirinu; here .. m . 

 U-ed, a proceeding by which, of COUrse, :i completely unnat ural 

 subdivision is ellected. In the (lep:i rt tire I'nmi ihe closed s|)ir:il. 

 :i ne\v (lii'ection of v:iri:it ion is ;i-Miine<l. :iini one is thrivt'oiv en- 

 tirely just ilied in making M division liere I'roni the old >tenis ; 

 for further subdivision, on the contrary, we must adopt few or 



no Characters derived from the tendency of va nation. The 

 sculpt mv is here hardly available, and indeed hardly at. all in 

 tin- beii-inninu- of the series of evolnte forms, but perhaps in the 

 farther stages, where an abnormal development and streiiirt heniniz 

 of ornamentation tends to take place. In this respect, the lobr> 

 will brst serve our pnrpo-e. since \ve lind amongst evolute foi'in- 

 :i -real number which present- exactly the symmetrical structure 

 ..f ili,- lbes of Lijluri-rua, whilst the others have eqiuilly dis- 

 tinct niisymmetrically divided lobes and saddles. 



Amongst the forms wliich jtresent symmetriciilly divided lobn- 

 fer structure, are Some, the uvoloincally oldest, which al-o ex- 

 hibit such striking agreement with /^///orr/v/.s 1 , that there can le 

 no doubt that 1he>e have descended from represeiital i \ es of that 

 Aside from the relations of the whorls, all other charac- 

 teristics of ,SVf/yi///7fs }'r/i,//>. further of Cri<n-ft'u.< A.<ti<'ri(inn in 

 and depreSKUm^ these au'i-ee mo>t completely with cretaceous 

 I.tll<>r<r<ilid;> . the first with L. recteCOStatum, the last withtlu- 

 irrnnp of Lijl. Ti inotlK'finii ni. \\\ >imple continuous develop- 

 ment of the spiral in the direction of variation, and of Course 



sing quite in the normal way from without inward-, we 



obi M in from tfi-fijihitt 1 * Yi'nnii the n-eniis /A/m/Vrx. from which 



differs only in the nio>t snbordinatecharacters. The 



impt-rfectly known ucnu- ras may al>o be must appro- 



* The rn-tacj-iiiis fonii-s .if A ///// 1'n'i'rn* ami ItiicuHim must lie 



into other genera, though <MH- could easily transfer their names to forma 



fn>m tin- middle .Iura>^ic, fur which otherwise new names would have Jo 



nne and unnulatum, Raculina 



