FOSSILS OF THE SILURIAN ANL> DEVONIAN ROCKS. 165 



Platyceras erectum, HALL. 



Acroculia erecta, Hall. Geol. Surv. of 4th Dist. of N. Y. 1843. 

 Platyceras erectum, Hall. Desc. of New Sp. of Foss., p. 4 1861. 

 Platyceras erectum, Hall. 15th Regent's Report, p. 4 1862. 

 Platyceras erectum, Hall, lllust. of Devon. Fossils, pi. 2 1876. 

 Platyceras erectum, Hall. Pal. N. Y., Vol. 5, pt. 2, p. 51885. 



Shell erect and slender. The spire at the apex is closely enrolled, for about 

 one volution and a half, beyond which the body-volution becomes somewhat 

 rapidly expanding, with the aperture often spreading. The specimens are 

 often more arcuate than their name indicates. The aperture is oblique, with 

 the peristome sinuate. 



The surface is marked by closely arranged, revolving, lamellose striae, which, 

 upon the lower half of the body- volution, are abruptly arched along narrow 

 bands, corresponding with former sinuosities of the aperture. 



Formation "and Locality. Occurs in the Corniferous limestone of the Devonian formation, at the 

 Falls of the Ohio, on Kentucky shore of river. 



Platyceras milleri. N. SP. 



Plate XXV., figure 1. 



Shell very elongate, forming a slender cone. Apex very minute, and closely 

 incurved for about one or one and a half volution; after this the shell is free 

 for about one and one-half volution. The whole shell increases very gradu- 

 ally in size from apex to aperture. The different volutions are separated 

 from each other by very large interspaces. The aperture is nearly circular, 

 and the lip is entire without sinus, but with very slight undulations. The real 

 shell is very thin. The surface is marked by fine, undulating concentric striae 

 or lines of growth, and, in well preserved specimens, with numerous slender, 

 tubular spines, which are seen when part of the matrix remains attached to 

 the shell. To a specimen of that kind before me are spines attached which 

 measure more than three-fourths of an inch in length. 



This species resembles, in regard to the number and size of the spines, 

 Platyceras dumosum, but its elongated form distinguishes it from that species 

 at the first glance. There is, in fact, no other species of Platyceras known to 

 me with which this one might be compared. 



Formation and Locality. I found three very fine specimens of this species in the Corniferous 

 limestone of the Devonian formation, at the Falls of the Ohio, on the Kentucky side of the river. 



It affords me great pleasure to name this elegant fossil In honor of S. A. Miller, Esq., of Cincinnati, 

 Ohio. There are very few palaeontologists in this country whose labors are of equal importance with those 

 o ' 8. A. Miller. His catalogue of fossils is an invaluable guide to all his co-laborers. 



