RAYMOND: NEW AND OLD SILURIAN TRILOBITES. 31 
panying the first use of the name niagarensis it would appear that Hall 
did not apply the name to the Wisconsin specimens alone, but meant 
to assign this name to all American forms previously ascribed to 
Cheirurus insignis or Ch. bimucronatus. This idea is strengthened 
by the fact that he states that the New York and Wisconsin specimens 
show the same characteristics. He also refers to Roemer’s Ceraurus 
bimucronatus from Tennessee. This idea is still further strengthened 
by the remark quoted above from his description of the Waldron 
fauna. If this is the case, then we should return to Hall’s first descrip- 
tion of a Ceraurus insignis in America to get at his idea of the species. 
If we take the other view, that the specimens from Wauwatosa, which 
seem to have been the first ones to cause Hall to doubt the correctness 
of his reference of all the Silurian cheirurids to the Bohemian species, 
are the real types of C. niagarensis, we are confronted by the fact that 
he did not describe his specimens, and, moreover, he was evidently in 
doubt about them, as evidenced by his pleasure at finding distinguish- 
ing features in the pygidia from Waldron. This latter description 
was the first real description published after the name niagarensis was 
proposed, and it might well be argued that the last described of the 
group should be the type. It seems simpler, however, to accept what 
was Hall’s evident intent, and believe that in proposing the name 
niagarensis he was merely proposing a new name for the specimens he 
had previously described as Ceraurus insignis. 
The first description of Ceraurus insignis Beyrich, by Hall occurs 
in vol. 2 of the New York State Paleontology, 1852. On page 300 
there is mentioned, without description, a glabella from the Clinton 
which is figured on plate 66A. On page 306 of the same volume Hall 
describes two cranidia from the Rochester shale at Rochester, N. Y. 
Both specimens are figured. As these are the first American speci- 
mens which are both figured and described, I propose to designate as 
the type of Chetrurus niagarensis (Hall) the one represented in fig. 10, 
pl. 67, of the above volume. This specimen is in the American Museum 
Natural History, No. 1827. 
The specimen so designated is a typical Cheirurus, with the glabella 
expanding rather rapidly forward, the frontal lobe occupying less than 
half the length of the glabella, and the first two pairs of glabellar 
furrows nearly straight, and following a direction approximately 
parallel to the posterior margin of the cephalon. Their inner ends are 
separated by a smooth space equal in width to about half the glabella. 
The eyes are near the dorsal furrows, and about opposite the second 
glabellar furrows. 
