Peridinium Cypripedium and Urocentrum Turbo. 5 
the same group that the Tintinnoidea border upon. The appa- 
rently low organization of some of the Peridinizea does not inva- 
lidate their approximation, through the higher forms, to the 
Tintimnoidea, any more than the inferior organization of the 
Cyclopidze depresses the whole class of Crustacea below the level 
of the group of worms. 
In this connexion I would mention that I do not believe that 
the so-called Cilio-Flagellata are distinct, as an order, from the 
Flagellata. I will not deny that the former, as well as the 
latter, have more intimate relations among themselves than exists 
between the two groups; but at the same time there are some 
(as, for instance, Prorocentrum) among the Cilio-Flagellata which 
hold their position there by a quite doubtful tenure—the few cilia 
at the anterior end indicating merely a preponderance in favour 
of their affiliation with that group, rather than a positive claim to 
be so united. The lorica gives to Prorocentrum the habit of a 
Peridinian, and may add a little to the strength of the argument 
which the cilia afford; but, on the other hand, there is a new 
genus of Infusoria which I have described in a recent work* 
under the name of Heteromastix (H. proteiformis), which pos- 
sesses all the habits, actions, mode of progression, and general 
appearance of a true flagellate infusorian, very much like a 
Heteromita, Duj., and is endowed with two anteriorly subter- 
minal flagella—the one acting as a proboscis or tentacular organ, 
and the other as a trailer or moveable keel; but at the same 
time the ventral anterior half of the body is hollowed out by 
a broad median furrow, which is thickly lined with locomotive 
cilia—thus presenting a peculiarity not heretofore deemed ad- 
missible as a characteristic of Flagellata, but, on the contrary, 
as appertaining alone to the Cilio-Flagellata. 
I would remark here, moreover, that in view of the fact that 
Peridinium Cypripedium possesses, beside the median transverse 
sulcation, an anterior annular furrow, and immediately in front 
of it a low skullcap-like covering, or pseudo-cuirass (both of 
which Mr. Carter appears to have been inattentive to in perusing 
my article), it seems possible that this infusorian may turn out 
to be generically different from any other Peridinian described 
hitherto. This looks so highly probable that I will propose the 
name Peridinopsis for it. 
Since my commentator has gone so far as to doubt even the 
specific diversity of these two infusorians, I would add, in regard 
to the species Urocentrum Turbo, that Ehrenberg describes and 
* ©Mind in Nature,’ by H. James-Clark, pp. 330, with over two hun- 
dred illustrations. New York, 1866. 
