CRUSTACEA. 
131 
greatest, with one long revolute appendage, which 
is ciliate on the outer side ; the internal with two 
appendages, which are ciliate on the inner side, 
ocular pedicles exposed to their bases, and distinct- 
ly triarticulate ; external maxillary feet involute, 
pediform, not closing the mouth, the basilar joint 
very stout, the rest longer, the third joint nearly 
cylindrical, and the terminal one subacute, external 
appendage produced nearly to the tip of the third 
joint, and rather strong ; feet strong, ciliate, their 
bases approximate, their edges sharp, and the tarsi 
falcate, anterior pair extremely large at base, hands 
didactyle. 
B. occidentalis. Mus. Acad. PI. VI. 
Testa polita, transverse impressa,lateribus utrinque 4-sph 
nosis, fronte trispinosa. 
Shell convex, somewhat obliquely elevated to- 
ward the centre, which is faintly carinate ; a median 
transverse sinuous impression, behind which the 
surface is polished, but anterior to it, densely mark- 
ed with small transverse impressions, most of which 
are pectinated and hairy ; a lateral transverse im- 
pression, and a very profound oblique one connected 
with it inferiorly; frontal edge strongly three- 
toothed, and excavated between the teeth ; a distinct 
post-frontal transverse groove, behind which is a 
strong tooth ; antero-lateral margin of the carapax 
with four stout teeth on each side ; posterior margin 
excavated ; second, third, and fourth pairs of feet, 
