SEOTIOISr II. 



LAMELLIBEANCHIATE SHELLS FROM THE PLASTIC CLAYS. 



The following five species of Lamellibranchiate shells are from the 

 plastic clays in the townships of Woodbridge, East Brunswick, and Sayre- 

 ville. These clays are supposed to hold a position stratigraphically below 

 the lowest of the green marls, and are consequently older, although their 

 true geological position does not appear to be very well determined. Some 

 of the layers of these clay beds furnish plant remains in large numbers, 

 many of which were submitted to Prof. L. Lesquereux some years ago, who 

 identified a considerable number of the species, and, basing his remarks 

 upon these plants, gave it as his opinion that they represented the flora of 

 the Dakota group of the West, Cretaceous No.l, of the Upper Missouri 

 section. I am not aware that any other opinion has been expressed of late 

 years as to their distinct equivalents in other parts of the country or in 

 Europe. In 1868 Mr. T. A. Conrad described two species of shells from 

 these clays and pronounced them Triassic (Am. Jour. Conch., Vol. IV, p. 

 279), stating that Professor Rogers had previously considered them as 

 forming the lowest part of the Cretaceous formation, but that he (Mr Con- 

 rad) had ascertained them to be Triassic. That they contained abundant 

 leaves and stems of Cydopteris. It will be seen by reference to Professor 

 Lesquereux's list published in the ^* Report on Clays" (Geol. Rept. N. Jersey, 

 1878, pp. 28 and 21^), that Professor L. does not include this genus among 

 those examined and reported upon. We may, therefore, consider that Mr. 

 Conrad may have been mistaken. Professor Cook also states, on page 29 of 

 the same report, that two specimens of shells only had then been collected 

 from the clays, and that these had been examined by Mr. W. M. Gabb, of 

 Philadelphia, who determined them to be CucuUcaa antrosa, Morton. I am 

 not sure that I have ever seen these two shells, but among all those which 

 I have seen, twenty or more, none of them would readily be mistaken for 

 that species. Imperfect casts of the one I have referred to G^nafhodon 



22 



