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. hivincronatus . 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 insigiiis 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 

 Jiiagarensis 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 Cheirurus niagarensis (Hall) the one represented in fig. 10, 

 pi. 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. 



