THEOEY OF RADICALS AND MORPHOLOGICAL EQUIVALENCE. 25 



Gal tortile, Gal. laqueum, and Schlot. catenata, in the Plicatus Stork- of T K 

 Anetjda, are more closely allied to one another and to P^"^ n are £e 

 morphological equivalents among their descendants to one another How 

 closely the descendant involute forms may simulate aTJ^fJ^Z 

 omc and nealogic stages are generally distinct, and indicate the ser ies wfth 

 ts peculiar differential characters. ^,,, mis eraUU or «JZ, TnT 7 

 Icengatum, are more nearly related to each other and to P 7 / T 

 jn th e L is gtock _ ^ of ^ d J^^« » 



lento There are several forms closely representative of one another and an 



Sf^r T^ am ° ng th6Se m -P^gical equivalent Tls the" 

 adults of Ver. Gonybean are apparently very closelv allied rn n n *• TV 

 and to some forms of Jrf. TurL .J Am L7 buf 111 of tf "' 



H^ d ^^^ 



lar tv I T' "T r* " ea '' ly re,ated in Stn '*' re »" d development, i„"h 11 

 lanty of he add sutures, the abseuoe of pite aud tubercles, and the mod of 



forms. We have elsewhere discussed this question, ami need" on.vTt fe we , 

 forlTGon-'tr " T" ^^"^ ^^ of Clydonantilns to t highe 

 toeT and off L r e '° "f diTMed VCn ' ral lobe > ° f Centroceraa to Apa- 

 tites and of Subclymenia to Agoniatites, and also the better known examrie 

 of the Clymemnm of the Devonian and the Atnria group of the Tertiarv Such 



expression, that these are mere analogies. This expression, however fills noth 



W occ a aZed ailsfn ^ ^'^ "^ « "» -* 

 nave occasioned and still occasion m our classifications, nor the constant ten 



fincy „f straight shells to become coiled and of already coiled di coTdd shells" 

 vhe P eTT>' Ve Se '' ,eS t t0 , beK " M "solute, to whatever series they may belong 

 libers!' y May ° aUi ' *" P1 '° dUCi " g ""^logical eouiva^ntst g g re :i 

 The only comparison that represents all these relations to my mind is that 



rZ^aJnT : are composed of groups, which, though distinct, 

 duced and in rt ' cl f' acter ' ste . « re nevertheless similar in the forms W o- 



oucec , and in the order of procession of these forms. 



n„ Jt ".I" 1 ™' 6 "'/ ™ 8 « f *« larger branches would be admitted to have orici- 

 also true m the smaller series, since in no case can the similarities of the 



