Cincinnatian and Lexington Fossils yy 



Orthoceras (Ormoceras?) hitzi, sp. nov. 



(Plate 1, fig. 3; Plate II, fig. 22.) 



Surface smooth when unweathered ; in weathered specimens, 

 longitudinal, flat, raised lines make their appearance. These seem 

 to be due to differences in the resisting powers of different parts 

 of the shell to weathering, or to the internal structure, rather than 

 to raised lines marking the inner surface of the shell cone. In 

 some specimens, these striae have a width of one-third of a milli- 

 meter. In others, their width is less. The number of longitudinal 

 striations varies usually between 6 and 9 in a width of 5 mm., but 

 greater numbers are found in some specimens. Orthoceraconc 

 rather small, gradually tapering. In a specimen 41 mm. long and 

 15 mm. wide at the larger end, the width at the smaller end is 9.5 

 mm. In this length there were 19 septa, of medium concavity. 

 The siphuncle is strongly annulated. The bead-like segments 

 equal in width about forty-three hundredths of the width of the 

 shell at its smaller end; at the constrictions where passing through 

 the septa the w^dth of the siphuncle is about half as great. The 

 cross-section of the shell is circular, and the siphuncle is more or 

 less excentric. The septa, as a rule, are symmetrically transverse, 

 but occasionally are oblique to the length of the shell, possibly due 

 to some physical defect of the individual animal. While the siph- 

 uncle is constricted in passing through the septa, a thin lamella, 

 having about the same curvature as the septa, appears to cross the 

 bead-like expansions about half way between the septa, and at this 

 elevation, in the upper part of the shell, the casts of the interior of 

 the bead-like expansions appears constricted in a manner somewhat 

 suggestive of Ormoceras. 



Compared with Orthoceras mohri. Miller, and Orthoceras 

 fosteri, Miller, the bead-like expansions of the siphuncle are much 

 wider. Compared with Orthoceras hallamiin, Miller, the bead-like 

 expansions are relatively wider and occupy a much greater part of 

 the width of the shell. Nothing is known of Orthoceras carleyi, 

 Hall and Whitfield, beyond the fact that the tube enlarges slowly, 

 there are about 6 or 7 septa within a length equal to the width of 

 the shell, and the specimen was found at Fayetteville, in Brown 

 county, Ohio, probably in the Waynesville bed. 



Compared with Ormoceras crebriseptnm , the exterior surface 

 of the shell appears smooth. 



Orthocei'as hitzi occurs in the Hitz laver in southern Indiana 



