56 A HISTORY OF RECENT CRUSTACEA 
ovate swimming organ. The species are marine or 
littoral. 
This legion contains four families—Cancride, Trape- 
ziide, Portunidz, Podophthalmide. 
Family 1.—Cuneride. 
The carapace is commonly transverse and convex, with 
the antero-lateral margins arcuate, and armed with several 
lobes, teeth, or spines. The ‘front’ is of moderate width, 
in general not projecting over the first antennee and the 
bases of the second, the latter being seldom excluded from 
the inner hiatus of the orbits. 
In this family are included about half a hundred 
genera, some widely and conspicuously distinct, others 
separated by fine and almost inappreciable differences. 
Thus Mr. Miers observes of Xantho (Leach, 1813), that 
‘it is connected by almost insensible gradations on the 
one hand with Lophoxanthus and Xanthodes, on the other 
with Panopeus and Hurypanopeus. Quite recently the 
genus Panopeus, H. Milne-Edwards, 1834, has been re- 
viewed by James Benedict and Mary Rathbun. They 
recognise in it thirty-eight species, and re-include within 
its boundaries Hurytium, Stimpson, 1859, and Hurypano- 
peus, A. Miine-Edwards, 1880, considering that they have 
been separated from the parent genus on grounds in- 
sufficient or untenable. It will, however, be quite be- 
yond the range of such a manual as this to enter into 
all the minutize of generic distinctions. Far less can the 
characters of innumerable species be discussed. Only the 
specially typical or the specially anomalous forms may 
court a passing attention. Here and there a comparison, 
a description, a comment, may indicate the variety of 
details upon which classification is founded, or may sug- 
gest the endless opportunities for the exercise of keen 
eyes and acute minds, which the subject provides. 
Those whose scientific zeal is limited to the desire of 
having the specimens in a cabinet rightly arranged and 
ticketed with their proper names are often puzzled and 
