ADDENDA. 489 



PHOLIDOPS. 



Among the fossils described in the second volume of the Palaeontology of 

 New-York, there is a Discina-like or patelloid shell, which I there termed 

 Orbicula squatniforrnis* . 



The shells heretofore referred to the Grenus Orbicula are properly 

 DisciNA ; and all the shells of this genus, which we know, have the dark 

 color and phosphatic composition of the recent species. The shell referred 

 to above, and other similar forms, are light-colored and calcareous in com- 

 position, and a farther discovery of similar forms proves them to have no 

 relation with Discina. It is not easy to determine whether these small 

 shells are bivalve brachiopods, or univalve like Capulus ; since the only 

 specimen seen, with two valves conjoined, admits of some doubt as to the 

 parts being in their natural relation to each other. From the resemblance 

 of the interior of one of these shells, and the flattened triangular space 

 beneath the apex, I had supposed them to have some relation with Crania ; 

 but in order to avoid any confusion, I have not adopted a name suggestive 

 of any such relation, which may after all be merely apparent ; and I would 

 suggest the name Pholidops, from the squamiform appearance of several of 

 the species. 



CiEKiJS Pholidops ( n. g.). 



Shells small patelliform : apex subcentral, excentric or terminal. Surface 

 marked by concentric lamellae of growth, which are more expanded 

 on the posterior side. Interior a shallow oval cavity, with bilobed 

 muscular impressions ; the margin flattened or slightly deflected, and 

 entire. 



• Palaeontology of New-York, Vol. ii, p. 250. 



[ Paljeontolooy III.] 62 



