270 
PALMOKTOLOGY OF NEW YORK. 
Orthoceras viator, n. sp. 
PLATE XXXVII, FIG. 5. 
Orthoceras baculum, Hall (in part). Illustrations of Devonian Fossils: Cephalopoda. Explanation of 
plate 37, fig-. 2. 1876. 
Shell straight, very gradually enlarging to the aperture. Transverse section 
circular. Apical angle 2b°. Initial point unknown. 
Chamber of habitation cylindrical, well developed, length five times the 
diameter at the last septum. The tube regularly and very gradually expands 
to a point near the middle, from which it gently contracts for a distance 
equal to one-fourth the entire length of the chamber; then expanding 
rapidly, and again constricting, it enlarges somewhat abruptly to the aper¬ 
ture. Air-chambers regular, so far as observed, having a depth of about 
four mm. 
Septa and siphuncle not observed. 
The test, as preserved on some portions of the tube, has had a thickness 
of 1.5 mm., and the exterior Was marked by fine lamellose lines of growth. 
The appearances of the internal mould with the double constriction of the 
outer chamber are very characteristic. 
A specimen, consisting of the chamber of habitation nearly entire, and 
two of the air-chambers, has a length of 104 mm., with a diameter of twenty- 
four and twenty-two mm., respectively, at the two extremities. 
This species is distinguished from 0. stylus, of the Schoharie grit, by its 
larger size and the constricted chamber of habitation. It more nearly resem¬ 
bles 0. exile, of the Hamilton group, but differs in its somewhat larger size, 
more cylindrical form of the tube, and much larger chamber of habitation. 
O. Telamon has comparatively deeper air-chambers, and has not shown evidences 
of a constricted chamber of habitation. 
Formation and locality. From the Upper Helderberg limestone at Clarence 
Hollow, Erie county, N. Y. 
