157 
process. The molar tubercle is nearly circular in section and 
owing to the curving of the basal portion of the mandible is of 
considerable length, the extremity is square-truncate and is thickly 
covered with short setae arranged in numerous rows running more 
or less parallel to one another across the end. Owing to the 
cutting edge of the mandibles projecting in one direction and the 
molar tubercle in another it is difficult to make a good drawing 
of them, to show all the parts and give a good idea of the arrange- 
ment of them. Figure 5 of plate xxiii., shows the left mandible as 
seen from above and a little from within so as to bring the teeth 
of the cutting edge into view. This part of the mandible projects 
downwards through the plane of the paper, while the molar 
tubercle extends obliquely upwards and is somewhat foreshortened 
in the drawing. 
The right mandible differs from the description already given 
in having no second or accessory cutting edge — in this respect 
resembling Asellus aquaticus. The next process crowned with 
strong seta* is present but appears to have the end narrower so 
that the setae are closer together and form two rows, one project- 
ing on each side ; the molar tubercle has the extremity oblique 
instead of square-truncate as in the left mandible. 
The mandibular palp is the same in both mandibles. It consists 
of three joints, the first is short being not much longer than broad, 
on the outer edge towards the end it bears a number of seta* and 
on the basal part of the mandible just posterior to the articulation 
of the palp is a small group of three sette. The second joint of 
the palp is about twice as long as broad, towards the distal end it 
bears several rather long sete in groups, some being on the outer 
margin and others on the under surface. The third joint is about 
two-thirds as long as the second, it is a little narrowed at the base 
and narrows also distally. The upper margin is rounded and free 
from sete, the under surface bears a double row of sette which 
gradually increase in length towards the distal end, the last two 
or three being considerably longer than the others and about as 
long as the joint itself. The sete in one row bear projecting teeth 
on one side, those in the other appear simple. 
From the description here given it will be seen that the man- 
dibles are not very different in form from those of Asellus aquaticus 
as described by Sars, the chief difference being that the seta) 
between the cutting edge of the base of the molar tubercle are 
placed on a raised base so as to form a distinct process, and are 
moreover somewhat different in character from those found in 
Asellus. 
The loiuer lip (Plate xxiii., fig. 6) consists of two rounded lobes 
somewhat widely separated distally and connected at the base by 
a flexible membrane fringed at the margin, and generally seen 
folded upon itself or puckered when the lip is removed for exam- 
