Mysidacea, Tanaidacea and Isopoda. 425 
Metasome. 
Number of 
Segments. 
Sutures. 
Zenobiana 
3-5 
(I) 
Pentidotea 
3 
I 
Engidotea 
2 
2 
Cleantiella 
2 
(2) 
Paridotea 
I 
3 
Glyptidotea 
I 
3 
Pentias 
I 
3 
Crabyzos 
I 
2 
We may complete the table by adding that the type species of Zenobiana has 
one suture on the metasome and, according to Miers' figure of Cleantis isopns, the 
type of the genus Cleantiella, this genus has two sutures on the metasome. 
It will be seen that the genera Paridotea, Glypidotea and Pentias are identical in 
the cliaracters so far noticed and it is difficult to see on what grounds they are 
separated. 
Cleantiella and Engidotea, which agree in the form of the maxillipedes and in the 
segmentation of the metasome, are distinguished readily by the flagellum of the 
second antenna which in the former is uni-articulate and in the latter, multiarti- 
culate. 
In attempting to place our species in one of the genera of this group we meet 
with our first difficult3^ It has four segments in the metasome, and one suture, and 
is therefore apparently referrable to the genus Zenobiana. But this conclusion is 
open to a good many objections which it is necessary to inquire into. 
Collinge's table of genera of the Idoteidae does not include the genus Cleantis, 
Dana. He presumably considers this genus as a synonym of Zenobiana, an opinion 
I have myself expressed previously. Cleantis was instituted by Dana in 1849 for 
the type species, C. linearis, Dana, captured off N. Patagonia. The genus and 
species were described and figured more fully in Dana's great work on the Crustacea 
of the United States Exploring Expedition. From that work, I have transcribed 
the following generic definition : — Outer antennae much the longer, not geniculate, 
five to six-jointed, without a flagellum. Feet of the fourth pair very much shorter 
than the third ; last four pairs gradually increase in length. Outer abdominal plates 
or opercula having a small lamina attached inside at the articulation. 
We may remark at once, that if Dana's type species really had uropods of the 
kind he describes (and his description is borne out by his figure, pi. 46, fig. 9k) none 
of the species subsequently added to the genus Cleantis have been correctly referred. 
No notice of this remarkable character of the genus Cleantis seems to have been taken 
by subsequent writers and I can find no reference to the form of the uropods in 
species referred to this genus except in the case of C. strasseni, in which Thielemann 
figures a uropod of the type more normally met with in Idoteidae, a flattened 
plate, divided by a suture near the distal end into a large proximal joint, the 
