CRUSTACEANS. 
485 
nuses. On the contrary, lie saw in the Crustacean a creature armed 
at all points, and he named it after the hero of his imagination. 
In this species the surface of the carapace is somewhat granulous 
'noth two denticles between the eyes, and three sharp points directed 
forward on each side. Ihe male has only five abdominal pieces, but 
the vestiges of the separation of the two others may be clearly re- 
marked upon the outer mediate or third piece, which is the largest of 
all. The length of the antennas are remarked on by Mr. Couch, in 
liis Cornish Fauna. “These organs,” he says, “are of some use 
beyond their common office of feelers; perhaps, as in some other 
Crustaceans, they assist in the process of excavation; and, when 
soiled by labour, I have seen the crab effect their cleaning by alter- 
nately bending the joints of their stalks, which stand conveniently 
angular for the purpose. Each of the long antenna) is thus drawn 
along the brush that fringes the internal face of the other, until both 
are cleared of every particle that adhered to them.” On the other 
band, Mr. Gosse suggests that the office of the antenna) is to keep a 
passage open for ejecting the deteriorated water after it has bathed 
and aerated the gills. “ I have observed,” he says, “ that, when kept 
m an aquarium, these crabs are fond of sitting bolt upright, the 
antenna) placed close together, and pointing straight upwards from 
the head. This is doubtless the attitude in which the animal sits in its 
burrow, for the tips of the antenna} may often be seen just projecting 
from the sand. When the chosen seat has happened to be so close to 
the glass side of the tank as to bring the antennas within the range of 
a pocket lens, I have minutely investigated these organs without dis- 
turbing the old warrior in his meditation. I saw on each occasion 
that a strong current of water was continuously pouring up from the 
Points of the antennae. Tracing this to its origin, it became evident 
that it was produced by the rapid vibration of the foot-jaws drawing 
m the surrounding water, and pouring it off upwards between the 
united antennal, as through a tube. Then, on examining these organs, 
I perceived that the form and arrangement of their bristles did indeed 
constitute each antennae a semi-tube, so that when the pair were 
brought face to face the tube was complete.” 
Among the numerous genera of Brachyurous Crustaceans, the 
Grapsidae are distinguished by their less regularly quadrilateral form ; 
the body nearly always compressed, and the sternal plastron but little 
