CEPHALOPODA. 26 1 



Test thin, ornamented by transverse stria? 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 been replaced by calcite, the remainder of the tube being filled and replaced 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. 



PLATI- WWII, FIG. I; CXII, FIGS. 9, 1». 



Ortkoctra* moltttmm, Mall (in part). Illustrations of Devonian Fossils: Cephalopoda. Explanation of 



plate 88, figs. 8, 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 <[uite 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 



