LINGULiE OF THE UPPER HELDERBERG ROCKS. 



Genus Lingula (Bkuguieke). 



Up to the time of commencing the printing of this volume, I do not 

 know of more than a single species of Lingula in the Schoharie grit, 

 and but two in the Upper Helderberg limestone. 



Several species occur in the limestones of the Lower Helderberg group, 

 and which have been already described ; but none are known to occur 

 in the Oriskany sandstone, and but three species between that rock and 

 the Marcellus shale or base of the Hamilton group. Collections of con- 

 siderable extent have been made, and over a large area of country ; and 

 judging from these, the shells of this genus were extremely rare in the 

 early epochs of the Devonian period in this country. The species are for 

 the most part rare in the Hamilton group, so far as my examinatons have 

 extended, and one only is known to be abundant. 



LINGULA OF THE UPPEE HELDERBERG GHOUP. 



Lingula ceryx (n.s.)» 



PLATE II. 

 A single specimen has been obtained, three-fourths of an inch in length 

 by half an inch in breadth. Very little of the shell is preserved ; merely 

 suflBcient to show that it was marked by fine concentric striae, with the 

 cardinal margin thickened. The cast has a distinct oval impression a 

 little above the centre, showing the mark of a muscular callosity at that 

 point. 



This species resembles in form the L. dknsa of the Hamilton group, but has not 

 the strong radiating striae of that species, while the subcentral muscular callosity 

 is also different. 



Except that this is the only representative of the genus known to me in the 

 Schoharie grit, I would not have thought it worth while to designate the species 

 from a single imperfect specimen. 



Geological formation and locality. In the Schoharie grit : near Clarksville, 

 Albany county, New- York. 



