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From the American Journal of Science and. Arts, 2nd. Series, Vol. XIIT.—Jan., 1852. 
GO b (^i 
ON THE my. p. ix | 
m d 
CLASSIFICATION 
OF THE 
CORYSTOIDEA, PAGURIDEA, rzrc. 
Bv JAMES D.. DANA. 
2 
l. Tur ConxvsroipEA have their closest relations with the Can- 
croidea, and form a passage between this division of the Brachyura and 
the Hippidea. "They are remote from the Oxystomata in the mouth 
and efferent branchial channels, the latter having these channels medial 
over the palate, and the former /ateral like the Cancroids. In the pro- 
jection of the outer maxillipeds over the epistome, the elongated and 
more or less pilose outer antennz, and the partially free or less closely 
inflexed abdomen, the species exhibit their degradation below the Can- 
cer type. "The Platyonychide are the Cancroids which approximate 
most to the Corystoids, and they are placed with this group by De 
Haan. But they differ from the Corystoidea in the shorter and more 
naked outer antennz ; and we therefore ineline rather to retain them 
with the Crancroidea, where they are arranged by Milne Edwards. 
'The degradation of the Cancroidea is also seen in another line lead- 
ing thrcugh Acanthocyclus to Corystoides, Lucas, and Bellia, Edw.* 
The last two genera are somewhat Corystoid in habit: yet they pertain 
to a distinct group, inasmuch as they have the outer antennz obsolete 
or nearly so, and the inner antennz without fossettes. "This last char- 
acter belongs only to the lower Anomoura and the Macroura, and places 
these genera quite low in rank in a group we name DBELLIDEA which 
belongs near if not among the Ánomoura. 
In attempting to arrange the Corystoidea into groups, we consider, 
as in other cases, the relations of the species to the higher Crustacea, 
and by the transitions observed, we are led to our subdivisions.  Tri- 
chocera is Cancroid in habit, in the absence of a beak, in the nearly 
naked outer antennze, and in having the outer maxillipeds fitted neatly 
to the epistome. | Zhia and Kraussia are also without a beak, like the 
Caucroids, but have the outer maxillipeds overlapping the epistome. 
'The remaining genera have the front somewhat rostrate, the inner an- 
tenne longitudinal, the maxillipeds produced over the epistome and 
the outer antennze elongate and pilose and flexed at base towards the 
medialline. "The form of the third joint of the outer maxillipeds varies 
from narrow oblong to transverse in closely related genera, and affords 
no basis for a family distinction. 
* In the synopsis of the Cancroidea in this Jour., vol. xii, p. 131, Corystoides was 
placed near Ácanthocyclus, to which it has close relations; but from this and the 
other Cancroids, it is remioved by the absence of all power of retraction in the 
inner antennze. Y 
'The name Aellia has been recently duplicated in the science, in an article by Mr. 
C. Spence Bate, on a new genus of Amphipods near Lepidactylis, published in the 
Annals and Mag. Nat. Hist., [2], vii, 318, sl. 11, f. 8, 1851. "The description of Milne 
Edwards's genus of this name is published in the Ann. des Sci. Nat. [3], ix, 1848, 
p. 192. 
SEcoND Sznrzs, Vol. XIII, No. 37.—Jan,, 1852. 15 
