104 
PALAEONTOLOGY OF NEW-YORK. 
This species is apparently identical with one in the Pentamerus limestone in the lower part 
of the group at Rochester. 
Fig. 3 a. A large specimen of this species, having a portion of the last volution broken off. 
Fig. 3 b. A smaller specimen, with the expanded portion of the last volution broken off. 
Position and locality. In a loose mass of gray sandstone of the Clinton group, New- 
Hartford, Oneida county. 
502. 28. ORTHOCERAS CLAYATUM (n. sp.). 
Pl. XXXI. Fig. 4 a, b. 
Cylindrical, rapidly tapering ; septa numerous, strongly arched ; siphuncle eccentric. 
Fig. 4 a. A fragment near the smaller extremity of the shell. 
Fig. 4 b. A smaller fragment preserving a portion of the outer chamber. 
The larger fragment has been much compressed, and in consequence the septa have an 
apparently oblique direction. The siphuncle is slightly excentric. -Several other fragments of 
the same species have been observed in the gray sandstone, but they are always denuded of 
the shell, and preserve no reliable features except the numerous and closely arranged septa. 
Position and locality. In. the upper gray sandstone of the Clinton group, south of Mohawk 
village, Herkimer county. 
503. 1. HOMALONOTUS DELPHINOCEPHALUS. 
Pl. XXXI. Fig. 5 a, b. 
For description, see Trilobites of the Niagara Group. 
The buckler ahd caudal extremity of this species are found in considerable numbers in this 
sandstone, though no perfect individuals have been seen. 
At the time these fragments were figured, I had not found this trilobite in a lower position ; 
but have since then obtained numerous fragments from the lower strata of the group, show¬ 
ing the existence of this species as early as the deposition of the ore beds, and probably from 
the commencement of this period. 
Position and locality. In the upper gray sandstone of the group, south of Mohawk village, 
Herkimer county. 
504. FRAGMENT OF ICHTHYODORULITE. 
Pl. XXXI. Fig. 6. 
This fragment of the defensive fin bone of some species of fish occurs in the sandstone 
with Pentamerus , Leptcena and Platyostoma , figured on the same plate. It is the earliest 
