CRUSTACEA. 
121 
Fam. GecarcinidcB. 
Germs Orthostoma. 
Testa convexa, margine carinata, lateribus sub-obliquis, 
valde curvatis; fronte depressa, dentata, acuta ; fossis ocu- 
lorum magnis. Maxillipedum articulo secundo intrinsecus 
producto; tertio interne exciso, apice acuto apud angulum 
externum articulum quantum gerente ore quadrato: anten- 
nis externis brevibus profunde insertis, hiatum internum 
baud implentibus. 
Shell longitudinally convex, with the margin 
strongly carinate, and more or less toothed ; sides 
of the body rather more oblique than in the neigh- 
boring genera, but far more vertical than in the 
Cancers; front depressed, having its edge thin, 
dentate, and not recurved; ocular pedicles not 
much elongated, cornea occupying only a small 
portion of their inferior side ; ocular cavities very 
large, rather irregular, and leaving an extremely 
wide space at the internal angle ; external antennae 
very short, having their basal joint deeply seated, 
while the terminal ones do not till up one-fourth of 
the orbitar hiatus ; internal antennae folded trans- 
versely in very narrow fossae, which are almost 
concealed under the front ; lateral pillars of the 
mouth straight ; external appendage of the maxil- 
lary feet slender, but not linear, and bearing a 
rather long palpus at its extremity ; second joint of 
the external maxillary feet produced antero-inter- 
nally, having the base of the third lying, for the 
most part, on its outer side ; third joint produced 
antero-externally, with the apex somewhat acute, 
vol. viii. — 1839. 16 
