ERRATA AND ADDENDUM. 



Page 55, line 15, for 1854 read 1855. 



Page 55, line 16, for Horticultural, read State Agricultural. 



Page 60, in second table, Illinois, for 240 read 241. 



Page 65, last line above foot-note, for ventricosa read ligann ntina. 



Page 72, line 9, for imbecilis read nnl><<-illix. 



Page 79, line 19, for asperimus read asperrimus. 



Page 80, insert Section Fusconaia Simpson, above Quadrula rubiginosa. 



