LOWER SILURIC SHALES OF THE MOHAWK VALLEY III 



species, but the evidence in regard to this character is not conclusive. 

 The surface sculpture exhibits revolving lines which are markedly 

 closer arranged than those of C . h a g e r i , where they are from 

 one to two millimeters apart, while here the larger ones are one 

 millimeter apart, but contain a smaller one between them. C . 

 h a g e r i possesses " strong angular ribs or undulations of growth 

 from half a line (i mm) to two lines (about 4 mm) apart becoming 

 more prominent with age. The Snake Hill form has on the older 

 volutions closely arranged subequal growth lines, which on the 

 last volution become gathered into elevated bundles of lines, the 

 middlemost of which are thicker and broader than the others. The 

 high folds on the type specimen are largely due to the lateral com- 

 pression of the shell. 



It will be noticed that our species stands in its characters between 

 C. montrealense and C . h a g e r i . The form from the 

 Jacksonburg limestone of New Jersey referred by Weller (title 53, 

 page 1 86) to C. montrealense, has also its revolving lines 

 farther apart than the Canadian type of that species and more 

 convex volutions, and may represent a fourth expression of the same 

 group. Its revolving .lines are of the character of those of C . 

 c u s h i ng i . 



Hyolithes pinniformis nov. 

 PI. 7, fig. 12, 13 



Shell small, slightly bent in proximal portion, expanding some- 

 what rapidly, one side flattened or slightly convex, the other with a 

 blunt median keel. The flat side is longer, projecting with an evenly 

 rounded lobe beyond the aperture, while the keeled side forms a 

 blunt reentrant angle. The surface is furnished with closely ar- 

 ranged sharp arching transverse striae (growth lines, which are 

 most distinct on the flat side; and with fainter longitudinal lines. 

 Operculum not observed. 



Horizon and locality. Canajoharie shale at Canajoharie, N. Y. 



Remarks. This species belongs to the group of Hyolithes s. str. 

 in distinction from the subgenus Orthotheca, Novak, according to 

 the character of its aperture. It is distinguished from the other 

 Trenton species of Hyolithes, save H . b a c o n i Whitfield, by its 

 more robust form. The latter species, from the Trenton of Wis- 

 consin is considerably larger and the apertural lobe of the flat side 

 is less projecting. 



