ANCEUS MAXILLARIS. 189 
the antero-lateral angles thus formed: within the place 
of insertion of the antennz on each side, the anterior 
‘margin of the head is somewhat porrected, and trans- 
verse, with a prominent tubercle on each side, the space 
between these two tubercles being emarginate, with a 
small prominence in the middle. The dorsal surface, of 
the anterior half of the head, is depressed, an evident 
channel running from the middle of the fore margin 
to the centre of the head, where it meets with a small 
posterior longitudinal carina, behind which is a very short 
transverse ridge (which may indicate the point of union 
of the two segments of the pereion soldered to the head). 
On either side, arising from the inner margin of the eyes, 
is a short slightly impressed fossa, the surface of which is 
more or less strongly granulated. ‘The superior antenne 
are about the length of the mandibles, slender, with two 
equal-sized basal joints, a longer third joint and a five- 
jointed flagellum reaching to the tip of the fourth joint 
of the lower antennz, which latter are nearly as long as 
the head and rather thicker than the upper pair, with two 
short basal joints; a third and fourth joint, more robust 
and of nearly equal length (equalling that of the third 
joint of the upper pair), and a short flagellum of six 
articuli. ‘The mandibles are of large size, being about 
two-thirds of the length of the head. They are nearly 
flat above, of asomewhat elongate-triangular form, with a 
prominent tooth in the middle of the outer edge, the apex 
prolonged into a curved tooth, and the inner margin armed 
with nine or ten small obtuse teeth; the inferior sur- 
face of the head is protected by a pair of large flat valve- 
like organs, each about half the size of the head itself 
(and which might be supposed to represent the second pair 
of gnathopoda (2), corresponding with the second pair of 
feet of the typical Isopods, but lettered g in the figures in 
