290 
ZOOLOaiGAl^ LITEJIATURE. 
the coasts of Sweden and Norway, and the family Tanaidae/^ 
It is chiefly on the family of the Tanaidae and the relation which 
it holds to that of the order of the Isopoda generally. 
The memoir commences with a summary of the previous 
history, from the period of Montagu’s description of Cancer 
gammarus talpa to the present time, including a consideration of 
Dana’s classification of this family, together with other Isopoda 
in which the three posterior pairs of pereiopoda only are directed 
backwards, into a separate tribe under the name of Anisopoda, 
and his own reasons for considering them true Isopoda, though 
differing ft’om the type. 
Of this genus TanaiSy in which he includes those of Lepto- 
chelis (Dana), Paratanais (Dana), and Crossurus (Rathke), the 
species are few ; and although the geographical range includes 
both northern and southern hemispheres, there have been but 
thirteen species recognized; to these, from the shores of Scan- 
dinavia, Prof. Lilljeborg has succeeded in adding nine new species, 
and believes that further research will add yet many more. 
He then gives a description of the family, and in the annexed 
table classifies the order Isopoda so as to show its position; 
but our own researches and observations preclude us from 
approving his classification. 
Though we cannot agree with Dana in the construction of a 
new group or tribe of equal importance with the Isopoda and 
Amphipoda for the purpose of receiving several somewhat ab- 
normal families in some of which there is rather a degradation 
than an alteration of structure, yet we think that he is correct in 
placing the Tanaidae very near to the Amphipoda. That he has 
placed the Bopyridae still nearer is an error that cannot vitiate 
the correctness of his judgment in relation to Tanais, of which 
we have had recent verification in observing that a pair of 
branchial sacs similar to those found in the Amphipoda are at- 
tached to the third pair of pereiopoda, thus demonstrating the 
near affinity of Tanais with the true Amphipoda. 
Isopoda. 
I. No fin tail. , 
A. The posterior pair of pleopoda sldhder and round, and 
1. Smaller than the preceding, and not squamiform. 1. Oniscid^^. 
2. Larger than the preceding ; more or less sqiiamiform. 
а. (Pleopoda) mostly branchial appendages. 
aa. No swimming feet. 2. AssELLiDiB. 
bb. The three posterior pereiopoda formed for swimming. 
3. Munnopsid-®. 
б. No branchial appendages. Five anterior paii-s formed for swim- 
ming. 4. Tanaid^. 
