ORISKANY FAUNA OF BECRAFT MOUNTAIN 39 



latter have the expression of Centronella more pronounced, while the 

 former suggest the genus Cryptonella. The former also have the beak 

 of the pedicle-valve the more erect. These two expressions, however, seem to 

 grade one into the other. One of the equiconvex shells retains a portion of 

 the interior of the brachial valve and shows the principal part of the loop. 

 There is an elongate hinge-plate which is perforate, and from its 

 anterior edge descend parallel or slightly divergent loop branches which 

 are reflected and upturned at their extremities as though to form an 

 ascending curve, but if this upward branch existed it has been broken 

 off, as frequently happens in Cryptonella. The aspect of the 

 apparatus is like that of the genus mentioned, save in this respect, 

 that the descending branches are cemented for their entire length to 

 the apparent floor of the valve. Both replaced shell and loop are 

 retained in silica and it seems probable that this attachment is wholly 

 due to excessive deposition of this substance. The species is not of 

 infrequent occurrence. There is an undescribed shell of very similar 

 character to this in the New Scotland limestone. 



Cryptonella, sp. nov. 



This species is represented by two imperfect specimens of a large, 

 convex pedicle-valve whose width is equal to or greater than its length. 

 The surface is somewhat elevated medially in the unbonal region of 

 one of the specimens, while in the other the valve is full and rounded. 

 Umbones depressed ; beak not conspicuous, erect. Surface highly punc- 

 tate with very low and fine radial plications. On the interior the 

 dental lamellae unite to make a short but slightly elevated spondyliuin, 

 in front of which is a short median septal plate. Length of the valve 



17 mm; width 21 mm. 



Rensselaeria ovoides Eaton 



Plate 5, flg. 17-19 



1892. Rensselaeria ovoides Clarke, op. cit. p. 414 



For other figures see Paleontology of New York. v. 3, pi. 104, 105 ; v. 

 8, pt 2, pi. 75 



Typical examples of this characteristic Oriskany species are quite 

 common in these beds. 



