CEPHALOPODA. 
26 7 
Test thin, ornamented by transverse striae of growth of varying strength. 
The surface-markings are well preserved over portions of the tube that have 
been replaced by calcite, the remainder of the tube being filled and replaced 
by the material of the surrounding rock. 
The specimen has a length of sixty mm., embracing a portion of the 
chamber of habitation and eight of the air-chambers. The diameter at the 
two extremities is thirteen and eight mm. respectively. 
This species is distinguished from 0. inoptatum by the position of the siphuncle, 
the greater distance between the septa, and the surface-markings. It furnishes 
some further evidence of the connection between the expanded siphuncle, the 
areolar extension to the ventral margins, and the carina or other markings upon 
the ventral walls of the casts of the air-chambers. 
Formation and locality. Upper Helderberg limestone, Clarence Hollow, Erie 
county, N. Y. 
Orthoceras inoptatum, n. sp. 
PLATES XXXVII, FIG. 1; CXII, FIGS. 9, 10. 
Orthoceras molestum, Hall ,(in part). Illustrations of Devonian Fossils: Cephalopoda. Explanation of 
plate 35, figs. 6, 8, and plate 37, fig. 1. 1876. 
Shell straight, regularly and gradually enlarging from the apex. Transverse 
section circular. Apical angle 5^°. Initial extremity unknown. 
Chamber of habitation regularly expanding to the aperture, without 
special characters. Air-chambers regular, having a depth of 4.5 mm. near 
the outer chamber. 
Septa smooth, thin, having but a slight concavity. Sutures straight and 
horizontal. 
Siphuncle quite excentric, showing evidence of a slight expansion between 
the septa. 
The test is thin, having a thickness of .1 of one mm. Surface marked by 
regular, sharp, continuous, longitudinal striae, about ten in the space of two 
