124 DR. L. A. BOREADAILE ON THE 
The lacinise are capable o£ independent movement. The outer moves to 
and from the middle line and also forwards and backwards in the body, and 
it combines these movements in varying degrees. The inner moves in and 
out of the mouth. 
6. The Mandihle is a short limb, whose proximal region or body is widened 
athwart the body of the crab and very strongly calcified. This region, 
which may represent either the coxa or precoxa, but is more probably both 
combined, is divided into two portions which it is convenient to know as the 
"head" and the "apophysis." The junction between these is marked by 
deep notches on the anterior and hinder sides and by an oblique, inflexible 
suture which joins them. The apophysis appears to run deep into the body, 
but it is in reality not interna) like the pieces of the endophragmal skeleton 
but an external structure, the true base of the limb, which pushes in the 
membranous body-wall till it comes to lie in a deep, close-fitting pocket. It 
presents to this pocket a convex anterior face and to the interior of the body 
a deeply concave posterior face. Ujjon its edges are inserted the muscles 
which move the limb. The head is much deeper from before backwards than 
the apophysis, and convex ventrally. It expands towards the middle line, 
where it presents to its fellow a sharp cutting or "incisor" edge, in the 
middle of which is an obsolescent tooth. Dorsal to the cutting-edge, in its 
concavity, is a low mound, the " molar process." External to this, also on 
the dorsal side, is a process with an outwardly facing concavity wliich- 
articulates with a knob on the epistome. External to the articular process, 
and still on the dorsal face of the limb, is inserted the palp, an inwardlj'- 
curved structure, which should be composed of three joints but actually has 
only two, because the first and second have fused. In the normal position it 
is folded back above the limb and almost hidden. The joints of the palp are 
flattened, the second more than the first. The limb articulates in front with 
the epistome, and behind is flexibly sutured to the sclerite which supports 
the metastoma. 
External to the base of the palp is a group of feathered hairs. The palp 
itself is bordered with rather long hairs, which are feathered at its base -but 
stout and simple at its apex. There is also a patch of sparse hairs on the 
ventral face of the apophysis. 
The musculatv/re of tlie mandible resembles that described for Cancer by 
Pearson. There are four muscles. A large outer adductor, inserted by a 
broad tendon upon the outer angle of the apophysis, arises from the subhepatic 
region of the carapace, and by its contraction must pull the end of the 
apophyais downwards and so bring its cutting-edge upwards and inwards 
against that of the other mandible. An inner adductor arising from the 
dorsal carapace is inserted by a very long tendon near the inner end of the 
mandible, which it must pull directly upwards. Two abductors, inserted 
respectively near the outer angle and on the posterior border of the 
