58 MR. T. BELL ON THE CRUSTACEA 
Pepipalpi externi rugosi, caule exteriore subulato, caulis interioris articulo primo canali- 
culato, exttis profundé emarginato ; secundo securiformi, tridentato. 
Pedes antici graciles, simplices, pari secundo breviores, digitis inermibus ; posteriores 
cylindrici, unguibus acutis, curvis, complanatis terminati. 
Abdomen Maris 7-articulatum. Famine... .? 
This genus offers in its general form and aspect, as well as in its more minute and 
important characters, several very remarkable peculiarities. The flattened body with its 
recurved and angular margin, the sloping direction and extraordinary size of the front, 
the laminated and extended form of the superior margin of the orbits, the absence of 
any inferior process of those parts, the eyes lengthened so as just to peep out beyond 
the extraordinary development of the orbits, whilst they are wholly uncovered beneath, 
the forms of the antenne and pedipalps,—altogether present a very interesting assemblage 
of characters, which, whilst they indicate a near affinity to the genus Criocarcinus Guér., 
show it to be essentially distinct not only from that but from every other genus of Crus- 
tacea. 
TyCHE LAMELLIFRONS. 
Tab. XII. Fig. 3. 
Hab. ad Panama, Americ Centralis. 
3 Mus. Soc. Zool., Bell. 
Carapax depressed, of an oblong irregularly four-sided figure, flattened behind the 
gastric region, which is considerably elevated and with the lateral and posterior margin 
forms a hexagonal outline: posterior margin turned up. The lateral margins are 
parallel, and anteriorly separated by a minute fissure from the superior orbitar process, 
which expands outwards, in a broad and flattened plate, covering the elongated eyes, 
so as to allow only the extremity of those organs to be seen from above ; it is curved 
forwards in a prominent flattened tooth which extends nearly to the level of the apew of 
the rostrum. The orbits are wholly wanting beneath. The rostrum is formed of two 
flattened teeth, separated from each other from its base ; they are obtuse, and excavated 
at the inner margin near the apex: both margins are furnished with hooked and cla- 
vated hairs. The eyes are smaller than their peduncles, which are elongated, somewhat 
larger at their base, gradually attenuated towards the apex, and wholly exposed from 
below, though concealed above (excepting at their tips) by the superior orbitar plate. 
The interior antenn@ are placed in an excavation at the base of the rostrum, which is 
partially divided by a small process of the anterior margin. Exterior antenne a little 
longer than the rostrum; the basilar joint broad, compressed, becoming rather narrower 
forwards, and having a very shallow longitudinal sulcus: the remaining joints cylin- 
drical, furnished on the outer side with numerous hairs, which are hooked at the extre- 
mity ; the second joint with a minute tubercle at its base; the third abruptly smaller 
than the preceding one. External pedipalps with the outer footstalk subulate ; the first 
