140 
CRUSTACEA. 
Fam. Alpheidce. 
Subgenus Atyoida. 
Pedum pare tertio elongato, gracili, coetera Atyae si- 
milis. 
It is essentially similar to the genus Atya, of 
Leach, excepting the third pair of feet, which are 
elongate, gradually retracted toward the apex, and 
scarcely stronger than the two anterior pairs ; the 
terminal joint is not broader at its extremity than 
the base of the tarsus. 
A. bisulcata. Mus. Acad. PL V., fig. 5. 
Testa polita, transverse sulcata, vnargineanterioriutrinque 
bispinosa, rostro producto, valde acuto, utrinquk bisulcato. 
Maxillary feet not attaining the extremity of the 
basal scales of the external antennae, which are 
densely clothed with black hairs at their extremi- 
ties, and greatly exceed the peduncle of the internal 
antennae ; thorax smooth, with a transverse sulcus 
behind the middle ; a spine on the anterior margin 
of the thorax, between the rostrum and the outer 
angles, which are also produced into a spine ; ros- 
trum commencing from the base of the front, pro- 
duced to a very fine point, and having a profound 
sulcus on each side ; the front is so much elevated 
on its margin, that the two sides, together with the 
rostrum, present, at first sight, the appearance of a 
triple carina ; terminal appendages of the abdomen 
smooth. 
Length about one inch. 
