534 Contributions to Invertebrate Palaeontology. 



exterior, but the outer volution, for a little more tlian the larger half, is 

 ornamented by a single series of comparatively large, transverse, triangularly 

 elliptical nodes on each lateral surface, having the angular side of the node 

 placed anteriorly and the opposite side nearly straight. The nodes are placed 

 at distances from each other about equal to one-half the dorso-ventral diameter 

 of the tube at the node indicated. The septa are not clearly defined and can- 

 not be given with certainty ; but they appear to be distantly placed on the 

 inner portions of the shell, while on the nodose portion they seem to be placed 

 at about half the distance of the nodes apart. The siphuncle has not been 

 observed. The surface of the shell, as seen on a fragment of the substance 

 remaining on the dorsum of the outer volution, is marked with rather close, 

 distinct, revolving lines or ridges, crossed by more closely arranged transverse 

 lines, which make a shallow retral bend in crossing the back of the sliell. 



The specimen is probably an immature shell, but is a distinctly 

 marked species, differing strongly in its form and nodose character 

 from any of those associated with it. It most nearly resembles G. 

 (Hercoceras?) paucinodus Hall, from the Upper Helderberg group 

 of New York (see Illust. Dev. Foss., pi. 55, figs. 1 and 2), but is 

 less distinctly triangular in a transverse section, that one being 

 widest near the outer portion of the volution, with a nearly regular 

 sloping surface on the side of the whorl to its junction with the 

 preceding one, while this species is rounded. The form of the nodes 

 is also different — those being situated near the dorsal margin. The 

 triangular form of these nodes is peculiar in having the two short 

 sides of the triangle directed forward. It also differs in having a 

 greater number of volutions for a given diameter. 



Formation and Locality. — In limestone of the Upper Helderberg 

 group, near Dublin, Ohio. Collected by Mr. Hyatt, of the State 

 University, at Columbus, Ohio. 



