CRUSTACEA. 
489 
verse; the fore margin semicircular; orbits with a slit above 
and below. 
Pirimela denticulata .— The Toothed Pirimela. 
Plate XCIII. fig. 9. 
Shell tubercular, each of the anterior sides provided with five 
teeth; three teeth in front, the centre ones largest. Inhabits 
the British coasts. 
Genns 17.—PORTUNUS.— Fabricius. 
Generic Character .—With medium sized exterior antennae, 
terminated by a setaceous filament, longer than the peduncle ; 
eyes distant, placed on short peduncles, inserted in lateral fur¬ 
rows under the front; shell broad, depressed, somewhat rounded 
anteriorly, and serrated ; the anterior pair of legs with forceps, 
the posterior pair terminated by an oval and ciliated plate. 
Portumis corrvgatus. —The Wrinkled Portunus. 
Plate XCIII. fig. 10. 
Wrinkled and granulated transversely, with five teeth before 
on each side; first and second joints of the claws with a spine 
on each; forceps serrated; hind legs with an ovate pointed ter¬ 
mination. Inhabits the European seas. 
Genus 19.—PORTUMNUS. —Leach. 
Generic Character .—Anterior pair of legs equal, with long 
forceps, the rest having compressed claws, dilated internally to¬ 
wards the base, the fifth pair with a depressed claw; shell with 
the transverse and longitudinal diameters the same. 
Portumnus variegatus .— The Variegated Portumnus. 
Plate LXXXII, fig. 11. 
With obscure granulations, and five teeth on either side, the 
second and third rather obsolete ; three teeth in front, and the 
wrists with one internal tooth. Inhabits the British seas. 
TRIBE III.-ORBICULATA. 
With an orbicular or ovoid shell, narrower before than be¬ 
hind, and generally with two furrows; third joint of the exterior 
feet-jaws triangular.—It contains five genera, namely: 20. Ma- 
