20 
HISTORY OF BRITISH CRUSTACEA. 
Pam. MAI ADM, M. Mw. 
Legs of moderate size ; the second and third pair never 
doable the length of the postfrontal portion of carapace ; 
first pair often longer and thicker than the following : ba- 
silar portion of outer antennae much developed. 
Gen. 4. ARCTOPSIS, Lam . * 
Carapace more or less triangular ; the front elongated 
and armed with four horns directed forwards, the two cen- 
tral forming a kind of beak. Eyes with short peduncles, 
which can be reflected in the orbits. Outer antennae with 
first joint narrow. Abdomen seven-jointed in both sexes. 
Eirst pair of legs in male much longer than the others. 
Pour hind pairs of legs with spines on the lower surface of 
the tarsi ; second pair of legs much longer than the third. 
Arctopsis tetraodon, Penn. sp. Four-horned Spider 
Crab . — Carapace a fourth longer than wide, posterior part 
regularly rounded, side with four strong spines ; third and 
fourth joints of fore legs tubercular. 
Carapace and greater part of legs covered with a dense 
coat of short hairs. 
* Pisa, Leach . 
