NOTES AND CORRECTIONS. 



GENUS PHOLIDOPS. 



In the Addenda to Vol. iii, Palaeontology of New-York, p. 489, I 

 have noticed and described a new genus under the name Pholidops ; 

 expressing some doubt whether it may be a patellifbrm univalve, 

 or a bivalve shell, since the only specimen where two valves were 

 shown in connexion was not entirely satisfactory. 



In the Thirteenth Report upon the State Cabinet, p. 92, I noticed 

 the genus, and described an additional species, expressing my belief 

 that the shell was univalve. The numerous specimens observed in 

 the Hamilton group are all of single valves; and hence I was led 

 to the conclusion, that in the Oriskany sandstone species, showing 

 two similar valves in contact, the relation was only accidental. 



During the last year, however, I have found among some collec- 

 tions from the Niagara group in Indiana, another species with two 

 similar valves closely conjoined; thus leaving no longer a doubt 

 regarding the bivalve nature of these fossils. The specimen here 

 referred to, and the Pholidops terminalis of the Oriskany sandstone, 

 have both valves entire, and there is no perforation as in Discina. 

 There may have been a foramen or opening between the valves at 

 the apex, for the protrusion of a pedicel. The description therefore 

 requires to be modified. 



GENUS PHOLIDOPS {as emended). 



Shell small, bivalve : valves patelliform; apex anterior, subcentral, 

 excentric or terminal. Surface marked by concentric lamellae of 

 growth, which are more expanded on the posterior side. Interior 

 of the valves a shallow oval cavity, with a bilobed or horseshoe- 

 shaped muscular impression in one of the valves; the margins 

 flattened or sometimes slightly deflected, and entire. 

 Shells known in the Niagara and Lower Helderberg groups, Oriskany 



sandstone and Hamilton group. 



