AMERICAN PARASITIC COPEPODA. 245 
The parts are somewhat difficult to study in the present species 
on account of its small size, but the main facts elucidated by Claus 
are found to obtain also here. I have not detected any labrum. 
The basal joint of the mandible is very large, and works in a some- 
what oval socket from which a chitinous ledge is continued forwards 
and outwards. The cutting edge is provided with several strong 
bristles. No palp is to be seen. The maxilla (mx., Fig. 15) is, 
however, more intimately attached to the mandible than in JL. 
Steboldii. That it is the maxilla, and not a mandibular palp, is 
shown by its articulation to a chitinous ledge continued forward 
from the socket of the maxillipede, and on which the basal joint of 
the mandible also partly rests. 
The second maxillipede is absent: the first 2-jointed and armed 
on the anterior and inferior faces of the lower joint with short, stout 
bristles. The maxillipedary sternum is particularly strong. 
THE NATATORY FEET, 
Except in details, which I have found to be constant, and which 
ought to be looked to for specific characters, the present species 
agrees with £. Sieboldii. The five sterna belonging to the five 
thoracic somites are constructed on the same type, and are formed of 
2 transverse chitinous thickenings continuous with each other at the 
sockets of the limbs. The sockets (a Fig. 16) project more or less 
from the surface of the body, and enter into the formation of a very 
free hinge-joint, with the basal segments of the limbs. These are 
also movably articulated to the posterior of the two sternal thicken- 
ings. The figure shows how the bristles and spines are disposed in 
the external and internal rami of the Ist natatory limb. The 
internal rami of the 2nd, 3rd and 4th pairs differ from that of the 
lst in having two bristles on the second segment instead of one, 
while the external rami of the 2nd, 3rd and 4th pairs differ from 
that of the Ist in the absence of the 2 spines on the terminal 
segment. The basal joint is not ciliated as in L. Steboldii. The 
natatory limbs of the fifth pair are represented by a bristle articu- 
lated to the end of the comparatively well developed sternum, 
I have not been able to determine the precise function of the 
curious chitinous structures situated at the opening of the oviduct, 
and which Claus has figured much more accurately than previous 
authors, They are evidently developed from the lining membrane 
