ORDER TRILOBITES. 
381 
broad, or broader, than long, presents, as in Asaphus and 
Ogygia, two oculiform eminences. The segments do not 
edge out beyond the body laterally, they are united as far as 
the end, and the body is terminated posteriorly in a sort of 
triangular and elongated tail. 
Tn Asaphus, Brogn ., the oculiform tubercles appear to 
present a lid, or are granular. The sort of tail which ter- 
minates the body posteriorly, is less elongated than in caly- 
mene, and either almost semi-circular, or in the form of a 
short triangle. Tn the asaphus of Brogniart , described and 
figured by M. Eudes des Longchamps, the posterior angles 
of the buckler, instead of being directed backwards, as in the 
other species, are recurved. 
The buckler of Ogygia, Brogn., is longer than broad, 
with the posterior angles elongated like .a spine. The oculi- 
form eminences present neither lid nor granulation. The 
body is elliptical. 
These! eminences having the appearance of eyes, do not 
exist, or do not at all appear in the genus Para doxi des, 
Brogn . The segments, or at least most of them, out-edge the 
body laterally, and are free at their lateral extremity. 
Such are the characters of the five genera established by 
M. Alexandre Brogniart, and which may be distributed into 
three principal groups; the reniformes , (genus Agnostus) 
the contractiles (genus Calymene) and the extensiles , 
(genera Asaphus, Ogygia, and Paradoxjdes). 
We shall refer, for the knowledge of the species and their 
localities, to the admirable labours of this naturalist, who, 
with respect to the fossil Crustacea, properly so called, or 
clearly recognized to be such, has associated with himself 
one of his first pupils, and a correspondent of the Academy of 
Sciences, M. Anselm Gaetan Desmarest, often cited by us, 
both for this part, and his work on the living Crustacea. 
