188 1> AL2E0XT0L0QY OF NEW YORK. 



A, figs. 11-14, are here recognized under this specific term, while figures 15 

 and 1G may perhaps be only varieties of the same species : the first of these 

 preserving obscure transverse markings, while the latter in one part is indis- 

 tinctly cancellated. 



Formations and localities. In the upper part of the Genesee slate near Bristol 

 Centre, Ontario county, and in other localities in central and western New York; 

 in the Cashaqua shales of the lower part of the Portage group on the banks 

 of the Genesee river, and in the same geological position near Ithaca, N. Y. 



CoLEOLUS CRENATOCINCTUM, n. Sp. 

 PLATE XXXn, FIGS. 1, 2, 3, AND PLATE XXXII A, FIGS. 3, 4. 



Shell an extremely elongated cylindro-conical tube, which tapers very gradually 

 from the larger extremity towards the acute apex. Section circular. 

 Shell substance comparatively thick and strong. 



Surface annulated by narrow crenulated rings, which appear to be directly 

 transverse. 



The largest diameter of the imperfect specimen, figure 1, plate XXXII, 

 is five millimetres, and at the smaller end approximating three and one-half 

 millimetres, with a length between these points of about four centimetres. 

 Another fragment in the same rock measures fully seven millimetres in 

 diameter. The longest specimen observed, and which, in the absence of 

 surface-markings, I have referred with doubt to this species, is about three and 

 a half inches in length. 



This species occurs in the higher beds of the Upper Helderberg group, and 

 in some localities it is quite abundant. The specimens, figures 1 and 2, plate 

 XXXII, are in a decomposing chert, and the shell is silicified ; a single 

 fragment only preserving the surface-markings, as represented in fig. 2. The 

 directly transverse aspect of the annulations may be due to the position of 

 the specimen, though we have no evidence of their oblique direction. 



In the specimen, figure 1, plate XXXII, the shell is shown to have been 

 replaced by layers of siliceous matter. The comparative diameter of the 



