364 
CLASS CRUSTACEA. 
Knorr. Monum. du Deluge, i. pi. xiv. Desm. Crust. Foss, 
xi. 6, 7. It would seem, according to these figures, that the 
lateral spines of the second piece of the testa, form only 
smaller teeth, instead of spines articulated by their base ; but 
these articulations have, perhaps, disappeared. 
Some have the four anterior feet terminated, at least in one 
of the sexes, by a single finger. 
We know but a single species of this division, which I have 
seen figured on the Chinese vellums, it is the Limulus hetero- 
dactylus , serving as type to the genus tachypleus of Dr. Leach. 
This limulus is probably the Kabutogani , or Unhid of the 
J apanese, and representing on their primitive zodiac, the con- 
stellation of Cancer. 
In the others, the two anterior claws at most, are mono- 
dactylous. All the ambulatory feet are didactylous, at least 
in the females. 
This division is composed of several species, but which, 
seeing the little attention which has been given to the de- 
tailed form of their parts, to the differences of sex and age, 
and of the localities which are proper to them, have not yet 
been characterized in a rigorous and comparative manner. It 
is thus, for instance, that the limulus, which is found com- 
monly in America, seen in its early age, is whitish, or of a 
flaxen colour, with six strong teeth, all along the crest of the 
upper middle of the testa, and two others, equally strong and 
pointed, on each lateral crest of the buckler, or of the first 
piece ol the testa ; while in the more aged individuals which 
are sometimes more than a foot and a half in length, the colour 
is of a very deep brown, or almost blackish, and the teeth, 
particularly those of the middle, nearly obliterated. Here 
again, the lateral edges of the second piece of the testa, have 
fine denticulations, which do not exist or are scarcely percepti- 
ble in the former. We shall refer to the young individuals, the 
Limulus cyclops of Fabricius, and the L . Sowerbii of Leach, 
