
No. 464.] STAGES IN LAGENIDA 553 
Senescent forms have been found among the fossils and to 
such forms Reuss has applied the generic name Dentalinopsis. 
In species of this genus the later growth instead of being tri- 
angular reverts to its earlier circular cross section and becomes 
truly Nodosarian. Reuss noted the generic value of this senes- 
cent character, although his genus has not always been recog- 
nized by later writers. The last-formed chamber may be more 
free and distinctly Lagena-like, thus completing the reversion 
in senescence. The formula for a specimen which has the 
Lagena-like last chamber would be L + N+R+N+L, 
showing its definite regressive senescence. 
