450 
ARTICULATED ANIMALS. 
In Asaphus, Brong’., the ocular tubercles appear to exhibit a covering, or are granular ; the tail-piece ter- 
minating the body, is less elongated than in Calymene, and nearly semicircular, or in the shape of a short triangle.* 
In Ogygia, Brong., the shield is longer than broad, with the 
posterior angles produced into a spine. The ocular promi- 
nences exhibit neither covering nor granulations. The body 
is elliptic. 
These eminences, having the appearance of eyes, either do 
not exist, or are not distinctly to be seen, in the genus Para- 
doxides, Brong. The segments, or at least the majority of 
them, extend laterally beyond the body, and are disengaged 
at their extremity on the sides. 
Such are the characters of the five genera established by 
M. Alex. Brongniart, and which may be arranged into three 
groups : 1, the Reniformes (genus Agnostus) ; 2, theContrac- 
tiles (g. Calymene) ; 3, the Extensi (g. Asaphus, Ogygia, and 
Paradoxides). We refer for a knowledge of the species and 
Fig:. 27.— A, Asaphus expansus. b, The same rolled up. respective Strata, to the work of the above-mentioned 
celebrated naturalist, who has associated with him, in respect to the fossil Crustacea, M. Desmarest, so often cited 
by us in our accounts of fossil and recent Crustacea. Other savans have proposed other genera amongst the 1 rilo- 
bites ; but being confined to the most general considerations, I can only cite those which appear in the best 
work yet published on these singular fossils. 
THE SECOND CLASS OF ARTICULATED ANIMALS FURNISHED WITH 
ARTICULATED LEGS,— 
ARACHNIDA,— 
Is, like the Crustacea, [composed of species] destitute of wings, and which are in a 
manner not liable to change their form, not undergoing metamorphosis, but simple 
sheddings of the outer covering of the body. Their sexual organs are placed at a 
distance from the posterior extremity of the body, being (except in some males) at 
the base of the venter. But they differ from these animals as weU as from the true 
insects in many respects. As in the latter, the surface of their bodies exhibits orifices 
or transverse slits, named stigmata (but which it would be better to name Pneumo- 
stomes,— mouth for the air,— or spiracles, that is, respiratory orifices), serving for the 
entry of the air, but being few in number, (eight at most, generaUy only two), and 
situated only on the under side of the abdomen. Respiration is effected either by 
means of aerial branchiae, serving as lungs and inclosed in bags, to which these 
spiracles form the entry, or by means of radiating tracheae. The organs of sight con- 
sist only of minute simple ocelli, grouped in different positions when there is a 
number" of them. The head, generaUy united to the thorax, merely exhibits at 
the place of the antennae two articulated pieces, like smaU didactyle or monodactyle 
claws, which have been injudiciously compared to the mandibles of insects, and so 
named ; but they move in a direction opposed to the motion of mandibles, or up 
and down, assisting, nevertheless, in eating, and replaced, in those Arachmda which 
have the mouth formed into a siphon or sucker, by two pointed plates, used as 
lancets.t A sort of lower Up {laUum, Fab.), or rather tongue, {languette) , formed 
* In Asaphus, Brongniart, described and figured by M. E. Deslong- 
charaps, the posterior angles of the shield, instead of being directed 
backwards, as in the other species, are recurved. 
t Chelicerae, or antennal claws, for such they are evidently, as 
proved by a comparison of these organs with the intermediate an- 
tennse of various Crustacea, especially those of the order Poecilopoda. 
Hence it is not quite correct to say that the Arachnida are destitute 
of antennae, a negative character, by which they have been defined 
by preceding authors. 
