48 RABENHORST AND GRUNOW, ON DIATOMACE. 
cessors ; and as the work of one who has long and attentively 
studied the subject, ought to be in the hands of every one 
devoted to this branch of algology. In some cases im- 
provements are made in the classification proposed by Pro- 
fessor Smith in the Synopsis, but we doubt that, as a whole, 
the species are divided into more natural groups, or that the 
work would prove as useful an introduction to the student 
seeking for a knowledge of the forms in any particular gather- 
ing as that of our fellow-countryman. 
The 9 sub-tribes of Professor Smith are divided into 15 
families, and the 59 genera he describes are extended to 71, 
though the whole number of genera included in the work 
amounts to 126, including such as Dictyocha, Cheetoceros, &c., 
which are considered doubtful members of the group by many; 
there are also included some foreign forms whose position in 
the arrangement is merely indicated. The work is only illus- 
trated by figures to mark the genera which appear to be 
similar to those in the Saxon ‘ Flora ;’? but they are inferior 
in execution to most of those of M. Grunow. We can, 
however, recommend both Dr. Rabenhorst’s and Grunow’s 
works to the careful consideration of the English student. 
