34 
PALAEONTOLOGY OF NEW-YORK. 
ORTIIOCERATA OF THE CHAZY LIMESTONE. 
Plate VII. 
Fragments of several species of Orthocerata have been observed in the Chazy limestone, 
though but few of them are sufficiently perfect to be identified from description. In general 
aspect, some of these appear to be identical with those of the Black-river limestone ; but 
there are others apparently peculiar to the Chazy limestone. 
59. 3. ORTHOCERAS RECTIANNULATUM ( n . sp.). 
Pl. VII. Figs. 2, 2 a. 
Cylindrical ; surface annulated by obtusely angular ridges, with broad curving depressions 
between ; annotations distant a little more than one-third the diameter of the fossil; 
siphuncle small, distinct, excentric; septa moderately convex. 
The septa are only visible on the extremity of the specimen, and being almost denuded 
of the shell, the character of the surface is unknown. 
Fig. 2. A portion of the fossil, nearly two inches long, exhibiting eight annulations. 
Fig. 2 a. Transverse section, showing the position of the siphon. 
Position and locality . In the grey crystalline central portions of the limestone at Chazy, 
Clinton county. ( State Collection.') 
60. 4. ORTHOCERAS SUBARCUATUM (n. sp.). 
Pl. VII. Fig. 3. 
Cylindrical, gradually tapering, slightly arcuated, marked by angular ridges which are 
equidistant and alternating with the septa; surface of shell smooth?; septa distant from 
£ to } the diameter ; siphuncle not visible. 
This fossil resembles the last, but tapers more rapidly, and the annulations are more 
acute. Another difference also is the slightly arcuate figure of the latter, which, if it be 
found constant, may characterize the species. 
Position and locality. In the central dark-colored limestone, associated with Maclurea 
magna , at Chazy, Clinton county. {State Collection .) 
