Explanation of Figures. 
Fig. I. Distyla ohioensis, sp. n. (p. 54.) 
Fig. 2. Diurella tigris, Ehr. (p. 49.) M, maxtax, egg, G. ganglion, s, 
sensory tube, spines of lorica, /, intestine, Pv. Pulsating vessel, eye. 
Fig. 3a. Ploesoma lenticulare, sp. side view. 
Fig. 3b. do. do. ventral view. 
ERRATA. 
Page 7, line i, instead of preceding, read proceeding, 
do 8, do 4, do do anteriorally, read anteriorly, 
do 15, Plate I, Fig. 2. instead of L, read f. 
do 48, line 7 .\, zw/mz/ ampuliformis ampulliformis. 
do 59, do I2-, do do Plate i, Fig. Ill readV\d.i% III, Fig. i. 
do 60, do 27, do do Asplanchnsea do Asplanchna. 
do 61, do 33, do do ampuliformis do ampulliformis. 
do 133, do 6, et seq. i-i read i-F. 
do 135, do Under monoelinic, instead of i-i and i-i, read i-F in each case. 
Table VIII, Apatite, instead of I,i readl.i. 
do /A, Olivine do do I=i 19° 2^ 1=130° 2^. 
do XI, Hypersthene, under cleavage, instead of conchoidal fracture i-i, 
read i-i. 
Table APT/. Instead of Tricilnic, Triclinic. 
do XVIII. Anorthite; cleavage, instead of \-l read i-i. 
