200 PALAEONTOLOGY OF NEW-YOKK. 



than in the last species, but still rounded. The transverse fine striae, under the magnifier, 

 give a kind of varicose appearance, being closely arranged and slight!)^ arched between 

 the longitudinal ones, following the oblique direction of the annulations. The difference 

 in the size of the longitudinal and transverse lines is a striking peculiarity of the species, 

 rendering it readily distinguishable from the last. 



I have referred above to the 0. calamiteum of Munstee, which, however, is from the 

 liio-her silurian or devonian rocks, from which circumstance alone it is proper to presume it 

 distinct from this one. The figure of Poetlock corresponds in some degree with our species, 

 but is represented with two or three finer longitudinal strife between the larger ones, while 

 the transverse striee are as strong as the fine longitudinal ones ; in which characters, the 

 one under consideration is quite different. M. de Verneuil has represented the O.calamiteus 

 as destitute of transverse strise ; though tlie one referred to that species by D'Archiac and 

 DE Verneuil, cited above, has transverse stria;. 



The species under consideration is not only quite distinct from 0. tiibkineUa of Sowerby, 

 Init from all the species in our higher strata, tliough having some resemblance to them. 



Fig. 2 a, b. View of two individuals, showing the annulations and longitudinal striK. 



Fig. 2 c. Transverse section of b. 



Fig. 2 d. Portion of the surface enlarged. 



Position and locality. In the lower shaly strata of the Trenton limestone at Middleville, 

 Turin and Lowville. A fragment or impression of the saine species has been found at an 

 exposure of the Trenton limestone one mile east of Alban}', which was incorrectly figured 



on Plate VII. (See page 35). (State Collection.) 



262. 15. ORTHOCERAS BILINEATUM, var. a. 



Pl. XLIII. Figs. 3 a, b, c, d. 



This variety differs from the typical forms, in the absence of the intermediate finer 

 longitudinal stricc ; the single series, which is pretty constant, corresponds in distance to the 

 coarser ones in tlie other specimens. A careful examination of several specimens, however, 

 has shown an occasional deviation from this rule, and smaller strife are sometimes present. 

 In otbiM- characters, it is not essentially different from the last, and therefore can scarcely 

 constitute a distinct species. 



Fig. 3 «. A fragment of this variety. 



Fig. 3 b. Transverse section, slightly compressed, showing the siphon, 

 Fig. 3 c. An enlarged portion of the surface. 



Fig. 3 d. A fragment denuded of the shell, showing the lines of septa wiiich do not correspond to tlu' 

 annulations. 



Position and locality. Same with the preceding. 



