234 PALEONTOLOGY OF NEW-YORK. 



are not observed upon the buckler or caudal shield, which preserves a double series of 

 punctures as shown in PI. 61, fig. 3 c. 

 Fio-. 2. This specimen has the crust almost entirely removed. The upper part of the cephalic shield has 

 been separated at the marginal suture, leaving the lower portion with the epistoma attached, as 

 represented m the figure. The position of the eyes is represented by the letters e e. This 

 interesting specimen was obtained by Mr. Bullions, Civil Engineer, from the Utica slate 

 on the Mohawk valley, and by him presented to the Cabinet of the Albany Institute. 



Plate LXIII. 



The lower figure represents the caudal shield, and five of the articulations of a very large specimen, from 

 the Collection of Mr. Moore, of Trenton Falls. The superior covering is removed, showing 

 the converging strife in the deep groove along the margin. This individual, when perfect, 

 could not have been less than nine or ten inches in length. The buckler is of nearly cor- 

 responding size. The narrow thickened border, and course of the facial suture, are well 

 shown in this specimen. The posterior angles are represented in the figure too much 

 rounded, the one from being broken, and the other from being covered by the stone. The 

 eyes are nearly perfect and remarkably prominent. 



Position and locality. In certain portions, particularly the bhick fine-grained layers, 

 of the Trenton limestone, this species is often abundant, though perfect specimens are 

 exceedingly rare. The bucklers, caudal shields, and fragments of the thoracic segments, 

 are met with in nearly every locality of this rock in the State of New-York. Beyond the 

 limits of New-York, we know of its existence in Canada, Ohio, Indiana, Kentucky and 

 Tennessee, being equally characteristic of the Lower Silurian rocks in all these places. In 

 our own State, it is occasionally found in the Utica slate and Hudson-river group, though 

 it does not appear to have flourished in these situations. 



In Ohio, one or two other species have been described as occurring in the lower strata ; 

 hut in no instance, within my knowledge, has it been found in any rocks above the Hudson- 

 river group. The species, therefore, and even the genus, may be regarded as eminently 

 characteristic of the inferior rocks ; and a single fragment, so far as our present knowledge 

 extends, is sufficient to decide the age of the rock in which it occurs. The more calcareous 

 nature of the older strata in their western extension, and perhaps other cavises combined, 

 have continued the existence of this species, in great numbers, long after it had nearly or 

 quite ceased in New- York ; and its remains characterize the higher portions of the Blue 

 limestone of Ohio, Indiana and Kentucky. 



