MOUTH-PARTS OF THE SHORE CBAB. 119 
their planes are now directed obliquely and meet ventrally at an angle. The 
articulation is, moreover, not absolutely rigid, and tlie movements rhay there- 
fore perhaps be modified by the small additional flexor miiscle described by 
Pearson. The merus, of course, shares the movements with the basi-ischium, 
but it is capable of a moderate amount of rotation upon its articulation with 
the latter. The rotation is oblique, from within outwards and at the same 
time dorso-ventrally. It is not conspicuous in the living crab, but it is used 
sometimes to lower only the distal half of th© operculum, and sometimes to 
give free play to the movements of the palp. The joints of that organ can 
move upon one another, but it is generally flexed or extended rather stiffly 
as a whole. It is so articulated that in extension it moves upwards as well 
as forwards. The flagellum of the exopodite is flicked outwards and inwards 
with very great rapidity, so that at times it cnnnot be followed by the eye. 
I have iilready alluded to the movements of the epipodite. 
2. The Second Maxilliped resembles the third in general plan, but differs 
from it greatly in appearance on account of the following features: — It is 
smaller, and its cuticle is thinner. In the endopodite,i\\Q basi-ischiopodite is 
short and its components are easily recognizable, the merus is very long, and 
both, though flat, like the rest of the limb, are narrow. Actually they are 
narrower than the last three joints, which are more flattened than those of' 
the third maxilliped. The exopodite is as large as that of the third maxil- 
liped, and much longer than its own endopodite. It is grooved to fit against 
the edge of the branchiostegite. Tiie epipodite is not hinged to the coxa, 
and a supporting rod of chitin runs from that joint along its anterior edge. 
It bears a long podobranch, and its distal part enters the gill-chamber, 
passes between its own arthrobranch and the anterior arthrobranch of the 
third maxilliped, and lies, like the epipodite of that limb, within the gills. 
The second maxilliped has the same relations to (lie sternum and epimeral 
region as the third, but is not connected with them by articulations like 
those of the latter limb. 
The second maxilliped is not outlined with hairs like the third, but a good 
deal of long hair is developed upon it, especially on the hinder face of the 
basal joints, on the epipodite, along the outer and towards the end of the 
inner edge of the merus, at the end of each of tlie hist three joints, and on 
the outer edge of the exopodite. The end of the last joint bears about eight 
very strong spines. The inner edge of the merus is not toothed. On the 
basal joints, and on the exopodite, the hairs are feathered. 
The musculature of the second maxilliped resembles that of the third, but 
the limb is more mobile. 
3. Tlie First Maxilliped is a thin, flat limb, covered for the most part with 
delicate cuticle, from which the majority of the articulations have dis- 
appeared. The coxa is a short, broa<l region, whose entity is established by 
