Zoology. 127 
4. POLYDECTIN/E.—Antenne interne transverse. Antenne ex- 
ternz basi solutze, liberee.—An Pilumnis propinquior ? 
G. PorvpEcrus, Édw.*—Orbita dentibus tribus infra instructa. 
Manus elongata, digitis prelongis, attenuatis, uncinatis, cum den- 
tibus tenuiter spinuliformibus sepe armatis. 
Faw. Il. ERIPHIDJE. 
Pedibus maxillipedeque 1mo Cancridis affnis. Palatum colliculo 
usque ad marginem anticum producto utrinque divisum. — Carapax 
sepius angustus, interdum latus, latitudine ante-medianá sepissimé ma- 
jore, oculis remotis. | 
1l. CETHRINJ/E.—Carapax transversus, lateribus valde dilatatus et 
rotundatus. Antenne interuz fere longitudinales. 
G. 1. CEruna, Leach. 
2. OZINAE.—Carapax plus minusve transversus. Digiti acuminati. 
Antenne interna transverse. —Orbita hiatu interno basi anténnz& oc- 
cupato instructa. Abdomen maris 7-articulatum. 
l. Articulus antenne externe lmus frontem bene attingens. 
G. 1. GarewE, De Haan.t—Carapax transversus, longitudinaliter 
multo convexus, antice declivis.—An .Potamie propinquior ? 
G. 2. Ozivs, Leach.—Carapax transversus, latus, fere planus. 
9. Articulus antenne externe lmus frontem non attingens. 
G. 3. PsEvpozius, Dana.i—Carapax transversus, fere planus, 
latior, margine antero-laterali breviore. 
G. 4. Pirumwvs, Leach.—Carapax angustus, parce transversus, 
sepius convexus, margine antero-laterali breviore. 
G. 5. PizuuNoipss, Edw. et Lucas.S$—Carapax angustus, parce 
transversus, valde convexus, margine antero-laterali longiore, 
bene arcuato, super carapacem postice incurvato. 
* This genus is very peculiar in the hand: both fingers are long styliform and 
very slender, with incurved apices, and hardly touching except at tips, and when den- 
tate the teeth are delicate spines on the inner margin ; moreover, the part of the hand 
anterior to the fingers is quite short. .À species collected by the writer is closely 
like the P. cupulifer in most of its characters. "The form of the hand is very unlike 
anything among other Cancroidea; and Halimede which has been supposed to be 
near Polydectus, has (like Medzeus) the ordinary form, like that in Xantho. 
The genus Zphiculus of White (Orust. Voy. Samarang, 5'i, pl. 13, f. 5), has the gene- 
ral characters of our Polydectus—the same villous coat, similar fingers, even to the 
spiniform dentation of the fingers, and other resemblances ; and we suspect although 
a broader species, that his 7. spong?osus is a true Pol'ydectus. 
The specimen of the Polydectus, from which a description with a colored draw- 
ing was taken by me while it was living, is not now found in our collections, and 
I have not therefore been able to ascertain the character of the przelabial plate and 
thus assure myself whether the species are related to the Eriphidze or not. Itis very 
possible that the true place is after Ozinz. 
1 Faun. Japon. 19. 
'$ Near Pseudocarcinus, from which it differs in the ridge on the prelabial plate, 
as well as in its flatter form. 
8 Crust. D'Orb. S. Am, 21. 
