Contributions to Invertebrate Palaeontology. 509 



field, Ohio ; associated with Aleristella bella, Nucleospira rotundata 

 and Leperditia alta, occurring sometimes in great numbers, almost 

 covering the surfaces of slabs. 



Genus SPIRIFERA Sowerby. 



Spirifera Tanuxemi. 



Plate V, figs. 4 and 5. 



Orthis plicata Vauuxem, Geol. Kept, 3d Dist. N. Y., 1842, p. 112, fig. 1. 

 Spirifera Vanuxemi Hall. 



The shells of this species are abundantly scattered over the sur- 

 face of certain layers of the Waterlime rock, at Peach-Point, Put- 

 in-Bay Island ; associated with Leperditia alta of Conrad, and 

 occur of all sizes from those of not more than an eighth of an inch 

 in transverse diameter to those of about five-eighths of an inch, and 

 present all the features of those of the Tentaculite limestone of 

 eastern New York. The form is transversely oval in outline and 

 convex in profile, on each side; the ventral being the most rotund ; 

 cardinal angles rounded and cardinal line short; ventral beak 

 strongly incurved. The shell is marked on each side of the mesial 

 fold or sinus by about four strong, rounded plications and are sepa- 

 rated by concave spaces, which on the ventral valve appear of about 

 equal width with the plications, but on the dorsal are narrower and 

 somewhat sharper in the bottom. The mesial fold is fully twice as 

 Avide as the strongest plication, is somewhat regularly rounded or 

 depressed convex, Avhile the mesial sinus of the ventral valve appears 

 narrow^er and deeply concave. The surface of the shell is marked 

 by fine transverse or concentric striae which are strongly undulated 

 in crossing the plications and fold, and under a magnifier are seen 

 to present considerable regularity in size and arrangement. 



The species presents many similarities to S. crispus Hisinger; 

 as it occurs in the Niagara group of New York and other places in 

 America, as well as to those of European localities. In fact it is 

 quite difficult to see wherein they differ, but as the Lower Helder- 

 berg forms are nearly always found only as separated valves and 

 more or less exfoliated, there is some difficulty in instituting satis- 

 factory comparisons. 



Formation and Locality. — In hydraulic limestone of the Lower 

 Helderberg group, at Peach Point, Put-in-Bay, Lake Erie. 



