CAPE COD GEOLOGY 



155 



sufficient to determine the division of the Matawan to which they should be 

 referred. If the Exogyra is correctly referred to Exogyra ponderosa, the deposits 

 certainly fall within the zone of Exogyra ponderosa. The stratigraphic limits of 

 this zone in New Jersey appear to correspond approximately with those of the 

 Matawan, though the lower limit of the zone has not been definitely established. 



The Cretaceous plants from Gay Head and Nashaquitsa cliffs are in sep- 

 tarian ferruginous concretions, which are similar to those that contain the inver- 

 tebrates, except that they are less hackly, splitting with smoother surfaces, and 

 the cavities appear to lack the drusy linings seen in the masses containing in- 

 vertebrate fossils. Most of the concretions are dark red, fine to medium grained, 

 and micaceous, and some are strongly micaceous. 



The plant-bearing concretions have been correlated by Hollick with the 

 Raritan ("Amboy clay") of New Jersey, but, as the invertebrate-bearing concre- 

 tions contain no fossil plants except an occasional obscure stem, the plants and 

 invertebrates were probably not derived from the same source. The two kinds 

 of evidence therefore do not necessarily conflict, the invertebrates probably 

 having come from deposits younger than the plant-bearing beds. If it should 

 be shown that the plant-bearing and invertebrate-bearing concretions were 

 derived from different beds in the same formation, the evidence of age afforded 

 by the plants would carry the greater weight, for the flora is large and well 

 preserved as compared with the fauna. 



FOSSIL PLANTS 

 The list of the Cretaceous fossil plants found on Marthas Vineyard given 

 by Hollick is reproduced below. (See Plate 21.) A list is also published by 

 Berry, 1 but this list includes also plants from Long Island and does not give 

 localities. So far as is known to the writer, only one addition has been made 

 to Hollick's list since it was published — Prepinus viticetensis sp. no v., described 

 by Jeffrey in 1910. 2 



Plants described by Hollick 



The plants named in the following list are described by Hollick: 3 



Gleichenia protogaea Deb. and Etts.? *Marsilea Andersoni Hollick 



Thyrsopteris grevilloides (Heer) 

 *Onoclea inquirenda (Hollick) 



Sagenopteris variabilis (Vel.) Vel.? 

 Podozamites sp. 



1 Berry, E. W., op. tit., pp. 615-618. 



2 Jeffrey, E. C, A new Prepinus from Marthas Vineyard, Proe. Boston Soc. Nat. Hist., 34, No. 10, 

 pp. 333-338 1910. 



3 Hollick, Arthur,, U. S. Geol. Survey Mon. 50, 1906. 



