PALEONTOLOGY. 419 



and also being the most prominent point of the valve, causes the rock to 

 adhere to the more abrupt sides when fractured, and gives to the valves 

 as they appear upon the fractured surface a very decidedly triangular 

 aspect, entirely unknown in L. alia. 



Formation and Locality. — In the hydraulic limestone of the Lower 

 Helderberg group, at Greenfield, Ohio, where it occurs in great numbers, 

 forming distinct layers through the rock, as does the L. alta in the 

 Tentaculite limestone of New York. 



SPECIES FROM THE LIMESTONES OF THE UPPER 

 HELDERBERG GROUP. 



PROTOZOA. 



Genus RECEPTACULITES DeFrance. . 

 Receptaculites devonicus. 

 Plate ii, fig. 10. 

 Receptaculites devonicus Whitf., An. N. Y. Acad. Sci., March, 1882, p. 198. 



A very decidedly marked and characteristic specimen of the genus 

 Receptaculites, DeFrance, has been obtained from the limestones of the 

 Upper Helderberg group, by Mr. Edward Hyatt, of the Ohio State Univer- 

 sity, from a quarry at Fishinger's mills, about eleven miles north of 

 Columbus, Ohio. The specimen is about two and a half inches in dia- 

 meter, is broadly concave across the disk, and slightly recurved at the 

 outer margin. The concentric lines of pores or cells are strongly 

 marked, and increase rapidly in size as they recede from the centre of 

 the disk, but the surface has been so much weathered that the grooves 

 left by the removal of the stolons at the foot of the cells are not distin- 

 guishable, so that the entire specific characters are not recognized; 

 enough, however, remains to show the general form and proportions. 

 It has much the appearance of specimens of a corresponding size of R. 

 Oweni Hall, from the lead-bearing limestones of the West, both in its 

 general form and in the concavity of the disk, as well as in the propor- 

 tions and rate of increase of the cell-openings as seen exposed on the 

 surface of the limestone. 



The occurrence of a species of this genus at this horizon, is a rather 

 unexpected feature in its history. The highest horizon of its occurrence 

 hitherto recorded, is in the shaly limestone of the Lower Helderberg 

 group of New York, from which the type of the species Receptaculites 

 infundibuliformis (Coscinium infundibuliformis Eaton, Geol. Text-book, 

 2d ed., 1833, p. 132, fol. 5, figs. 64, 65), was derived. The figure and 

 description, as given by Prot. Eaton, are both poor, but the specimen is 

 still in the cabinet of the Rensselaer Polytechnic Institute, bearing the 



