300 
PALAEONTOLOGY OF NEW-YORK. 
666. 3. PHACOPS TRISULCATUS. 
Pl. LXVI. Fig. 3 a, b. 
Calymene'! trisulcata. Hall, Geol. Rep. of 4th District N. York, 1843, pag. 72, fig. 9 ; des. p. 74. 
Compare Phacops ( Calymene']') Downingia, Murchison, Sil. System, pag. 655, pl. xiv, fig. 2. 
Buckler semicircular, posterior angles obtuse ; front rounded ; glabella lobed, the divisions 
angular, separated by narrow sharp grooves; eyes small; caudal shield short, with few arti¬ 
culations; surface! 
The only specimen of this species which has fallen under my observation is the small one 
figured, and in this the surface is partially crushed and the markings obliterated. The divisions 
of the glabella correspond with P. downingice , but the front of the buckler is more rounded 
and the caudal shield shorter. It is possible, however, that larger and better preserved speci¬ 
mens may show a more intimate relation between the two. 
Fig. 3 a . The individual of the natural size. 
Fig. 3 b. Enlargement of the buckler, several ribs of the body, and the caudal shield; in which 
the characters are distinctly represented as seen under the magnifier. 
Position and locality. In the upper green shale of the Clinton group, associated with 
Jltrypa hemispherica and Leptcena corrugata. 
667. 5. CERAURUS INSIGNIS. 
Pl. A LXVI. Fig. 4. 
Cheirurus insignis. Beyrich, Ueber einige bcemische Trilobiten, Berlin, 1845. 
See page 306 of this volume. 
The discovery of the fragment figured on this plate was the first indication I had of the 
existence of this genus in the upper silurian strata. The imperfect heads of two other individuals, 
from the shale of the Niagara group, have since been obtained. 
