CHAZY LIMESTONE. 
25 
This is a very distinctly marked fragment of an undescribed trilobite ; the distinctness of 
the false articulations, and deeply trilobate character of the caudal extremity, distinguish 
it from known species of Isotelus, which it resembles in the marginal expansion and general 
form. 
Position and locality. This fossil is found in the crystalline and highly fossiliferous mass 
of the Chazy limestone, below the portion containing Maclurea magna, at Chazy village. 
(State Collection.) 
43. 1. ISOTELUS GIGAS? 
Pl. IV. (bis). Fig. 16. 
Asaphus platycephalus. Stokes, Trans. Geol. Soc. London, 1822, Second series, Vol. i. p. 208, pl. 27. 
Isotelus gigas. Dekay, Annals N. York Lyceum, 1824. Vol. i. p. 174, plates 12 & 13. 
This fragment approaches so nearly in character to the caudal shields of the young of 
Isotelus gigas, that I have not thought it worth while to separate it from that species. 
44. 2. ISOTELUS CANALIS. 
Pl. IV. (bis). Figs. 17, 18, 19. 
Isotelus canalis. Conrad in MS. 
Margin of caudal extremity broadly and deeply depressed, forming a channel ; surface 
punctured. Judging from this fragment, the original was at least six inches in length. 
Figs. 18 &. 19. Labrum or epistoma of an Isotelus , perhaps of I. canalis. 
The structure and * general aspect of these portions of the trilobite evidently ally it 
generically with the Isotelus ; and from the discovery of these, I am disposed to admit 
the species which the fragment before mentioned did not justify. The form of these plates 
is more elongated, and totally different from the corresponding parts of I. gigas. 
Position and locality. These fragments of a large species of Isotelus occur near the 
upper part of the mass, a little west of Chazy village. ( State Collection.) 
45. 1. CERAURUSI — ( Species undetermined ). 
Pl. IV. (bis). Fig. 20. 
A single fragment, being the posterior prolongation of the buckler of a species of 
Ceraurus, very analogous to C. pleurexanthemus of the Trenton limestone. 
Position and locality. In the oolitic limestone of Chazy. {State Collection.) 
Remains of other trilobites, too indistinct to be described, have been noticed in this rock ; 
but the materials are so comminuted, that it is impossible to recognize fossils, of which 
fragments of many species have been observed. 
[ Palaeontology.] 4 
