JS'^ctr Species i)f Fui<sils f rum Ohio. :203 



lanceolate, with the dorsal portion rising into a thin, sharp crest or ridge ; 

 anterior side rounded and the anterior slope concave. Aperture narrowly 

 ovate, rounded on the anterior side, widest just above the middle, and ex- 

 tending backward into a narrow point. Surface of the shell marked by 

 line hair-like concentric lines of growth parallel to the margin of the aper- 

 ture, wdiich is a little bent down anteriorly and posteriorly, and also by a 

 rather faintly marked, but still distinct sulcus, which passes from the apex 

 on the left anterior slope, and over which the strite are slightly undulated, 

 indicating a slight notch m the margin at this point. 



Ill the narrow cirid curved lanceolate form of the shell, this 

 species differs very materially from any of the numerous species 

 of this very monotonous genus, and maybe readily distinguished 

 by the sharp dorsal ridge. 



Formation ami Locality. — In the Upper Helderberg lime- 

 stone, at Columbus, Ohio. Collection of Columbia College. 



Dentalium JMariini, n. sp. 



Pal. O., Vol. Ill, Plate 8, Fig. 10. 



Shell somewhat larger than medium size, rather rapidly expanding from 

 the apex to the aperture for a species of this genus, and moderately curv- 

 ing throughout the length ; cylindrico-conical in form, and circular in a 

 transverse section. Surface marked only by encircling striae, which form 

 rather broad undulations on the shell, and are strongly arched forward on 

 the inner side of the curvature, showing that the lip of the shell has been 

 somewhat extended on this side of the aperture. Shell-substance thick. 



The species attains a rather large size, and expands more 

 rapidly than most species of the genus, reaching a diameter of 

 one-fourth of an inch in a length of less tliau two inches. Tlie 

 curvature is also considerable, being deflected fully an eighth of 

 an inch from a straight line within the length of the sjjccimen 

 when tested on the inner face. There is no species of similar char- 

 acter from rocks of Devonian age, so far as can be ascertained. 

 On some of the internal casts, there occurs a longitudinal ridge, 

 as if there had been a slit or interruption of some kind at that 

 point, which gives rise to a supposition that it may have belonged 

 to the genus Coleopi'ion, Sandberger, though no positive inter- 

 ru]3tion of the strise of the surface is seen on any specimen ex- 

 amined. This fact may suggest its belonging to the recently 

 formed genus Coleolus, Hall, but its perfect resemblance to 

 Dentalium more strongly indicates its affinities as in that relation, 

 rather than wdth the Pterojioda, Nor does there appear any 



