C \ I LGES 



gibbous; 1 that is, after the quadragona] whorl lia<] appeared in the development 

 of the nine individual. 



\\ • have also Bhown thai in every Beries similar changes te,"k place in the 

 and were accompanied l>\ a correlativi 

 give pathological changes in the keel, channels, pila), tubercles, and sutures. The 

 eonvei Fore, a retr character when it occurs 



quadragona] whorl has appeared either in the evolution of 

 i in the development of the individual. In Bsil I con- 



if the sides <>f the whorls was present, and was a primitive character 

 of the helmet-shaped whorl, and this occurred also in Arn. and in the 



her forms of the Levis Stock. Such characters in the indi- 

 viduals of radical Bpecies occur before the quadragona] whorl is developed, and 

 in connection with primitive radical characteristics and forms which will n«>t be 

 confounded with geratologous characteristics and forms by any close observer, if 

 be have sufficient materials for Btudy. 



There is a true senile degeneration in the old age of Bome forms, which is 

 apparent in the marked convergence of the rides and sub-acute abdomen of the 

 old whorl, even in such discoid al species as the /'-//. plevrolissum} This, as a de- 

 itive character, was reproduced at an earlier neal< in the involute 



by comparing these figures with those of the involute 

 : /' I - me law holds also in Wsehneroceras. In Schlo- 



theimia it becomes apparent when we compare tin' old age of Schlot. < 

 having smooth abdomen and convergent smooth .-ides, with the side- and abdo- 



■ which are -imilar in the nealogic and ephebolic si 



Such char ve, and indicate decline in so far a- the 



of tin- whorls, the pila*, and the channels are concerned, notwithstanding 



th>- fact that th a correlated with the progressive character of gi 



involution, and appear in the nealogic stages of some (geratologo I' 



will be observed that, in ( from the Mediterranean province, 4 the com- 



\\1imi] and other degenerative characteristics occurred without a 



irtionate in involution, and that the same phenomena occurred also 



ice of tli. evidently a geratolo e in Caloci 



and Venniccras, but in some species of Amioceras a Blight tendency ofthi 

 nt in the adult Rtngc was noticed In I 

 rred in tin- adult stage of varieties with well developed keels, 

 channels, ami pila?, but not so noticeably in the lower varieties "i '!• 



, development In I /-' where it was found in all 



ind in the -tdl more highlj 

 I development of the involute l very much earlier than 



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