Zoology. 123 
"Ruppellia of Edwards, and Eudora of De Haan, have the same 
typical species. But De Haan neglected to observe in the type the 
important peculiarity of the orbit, (its being wholly closed within so as 
to exclude the base of the outer antenne, a peculiarity found in no 
Brachyura except a few of the Eriphidze,) and hence his genus includes, 
according to his own use of it, some Xanthoid species. "l'he two names 
are by no mears synonyms; and adopting the group as laid down by 
Edwards, we are forced to adopt his generic name. — Modifications to 
some extent may be made in accepted genera, and this we have at- 
tempted in some instances below, but not the complete perversion that 
would happen by giving De Haan's name to Edwards's genus. 
De Haan has not recognized the distinction between the pointed and 
spoon-shape figures as a generic characteristic, and this makes some 
difficulty in substituting his names for those of Edwards, where the 
groups are otherwise similar. "This characteristic was first employed 
by Leach and subsequently by Edwards. "The genera of the two kinds 
often graduate into one another: but the parallel relation between the 
series is best shown by retaining them apart in separate subfamilies. 
Between our Xanthinze and Chlorodinz there is nearly a perfect paral- 
lelism. De Haan's species of the genus Xantho are in part Chlorodii. 
De Haan has multiplied much the genera of swimming Crabs, by 
subdividing Lupa and Thalamita. This has partly arisen from an un- 
warranted reliance for the characteristic on the form of the 3d joint of 
the outer maxillipeds, as well as on that of the inner branch of the 1st 
maxillipeds. 
In a former paper it was observed that the 3d joint of the outer max- 
illipeds may undergo great variations in proportion in the same genus. 
This is well illustrated among the Portunide. — Amphitrite of De Haan 
(a subdivision of Lupa) is described as having this joint short and ob- 
lique. But in species of true Amphitrite, it varies from this form to a 
form unusually oblong. Again he makes Neptunus and Achelous 
differ from Amphitrite in having this joint more oblong, the reverse of 
. which is actually the fact among many of the species examined by the 
writer. So Thalamita is characterized by having this same joint 
short, when in fact it is sometimes longer than broad. The form 
in one species (T. integra, D.) scarcely differs in relative length or 
obliquity from that of Lupa dicantha. Again Oceanus (Thalamita 
crucifera of Edwards) is said to have the inner branch of thé 1st max- 
ilipeds three-lobed, and Thalamita, as. having the inner margin uni- 
dentate. "'l'he latter has the inner lobe as in Oceanus, and this makes 
the one tooth ; the margin outside of this lobe or tooth, is straight at top 
in some species (T. crassimana and crenata), but excavate in others, 
becoming even deep and angulate in T^. integra, a species very near 
admetus in form and general characters. "There is thus a gradual: 
transition to the form in Oceanus. Such variations in this margin are 
therefore unimportant, as many other cases illustrate. 
Our grand divisions are named after the larger to which they ap- 
proximate. "This plan might be carried farther with much profit. 
Thus among the five families of Cancrinea—the Cancridz, are the 
Cancrinea Typica ; the Eriphidze, are the Cancrinea Grapsidica, for in 
the ridges of the palate as well as form they approximate to Grapsus ; 
