NEW SPECIES OF GONIATITID^E. 133 



deep and acutely pointed, while in complanatus it is rounded. 

 It differs from 0. Nwndaia in the rounding of the ventro-lateral 

 lobe, while in that species both lobes are acutely pointed. 



Formation and locality. — In the lower part of the Chemung 

 group, at Homer, Cortland county, and near Truxton, N. Y. 



GONIATITES UNILOBATUS Hall. 



Shell, rather below the medium size, subdiscoidal ; volu- 

 tions, three or four, deeply embracing, leaving only a moder- 

 ate open umbilicus, in which is seen only about one-fourth or 

 less of the inner whorls ; the volutions are flattened or slightly 

 concave on the dorsum, which is about a twelfth of an inch in 

 width on a specimen of one inch diameter ; sides gently swell- 

 ing from the subcarinate angles of the dorsum to near the 

 inner border, then abruptly rounded into the umbilicus. 

 Septa moderately distant ; four chambers occupying a space 

 equal to the width of the volution at the part measured. 

 From the margin of the umbilicus, the septa curve gently 

 backward, and then forward with a broad curve, reaching 

 their greatest anterior extension a little within the dorsal 

 angle ; from there they bend abruptly backward and form a 

 narrow dorsal lobe slightly truncated at the extremity, giving 

 a single broad lateral lobe extending nearly the width of the 

 volution. 



Surface marked by fine, even, distant thread-like striae, 

 with curvatures nearly in the direction of the septa, but with 

 the flexures not quite so extreme. 



This species differs from all others noticed from the rocks 

 of New York, in the form of the septa and the flattened 

 dorsum. 



Formation and locality.— In the Hamilton shales, from the 

 shore of Cayuga lake, N. Y. 



GrONIATITES SIMULATOR Hall. 



Shell of medium size, consisting of three or more moderately 

 convex volutions, which are closely coiled, leaving only a 

 moderate, rather abrupt umbilicus, but slightly exposing the 

 inner whorls. The volutions are thickest near their inner 

 margins, from this they gradually decline with a rounded sur- 

 face to the narrowly rounded back. Septa closely arranged 



