Professor Eaton has proposed the name Brongniatia (Brongniartia?) for a
genus of trilobites, which we think he has not defined with sufficient
accuracy to be of any practical use. The _Isotelus gigas_ of Dr. Dekay,
which has been for a long time so well established, is here ranked
merely as a species under the name of B. isotela. The relic which we
described before the Geological Text Book appeared as the _Triarthrus
Beckii_, forms the species B. carcinodea--and the trilobite which is
supposed to be the Asaphus platycephalus of Stokes, is the only other
species mentioned. The A. platycephalus,[48] we know to be identical
with the I. gigas, and as the animal remain described by Mr. Eaton
is entirely different from Dr. Dekay's fine species, we subjoin the
account given in the "Text Book."
[Footnote 48: For a figure and description of the Asaphus
Platycephalus, by Mr. Stokes, see Transactions of the Geological
Society. Second Series, vol. i.]
Genus Brongniatia--Fore abdomen always, and post abdomen in some
cases, longitudinally divided into three lobes, by regular series of
undulations traversing the joints, without grooves; articulations of
the side lobes being manifest continuations of those of the middle
lobe, and consequently, agreeing in number.