THE MARSHALLTOWN. 89 



and Qstrea falcata of the Marshalltown being replaced by Hxo- 

 gyra costata, Gryphaea convexa, and Ostrea mesenteries in, the 

 higher fauna, although G. convexa has been rarely observed in 

 the Marshalltown, and 0. falcata in the Mount Laurel-Navesink. 

 The same species of Gryphaeostrea, G. vomer occurs in both 

 faunas. Besides these oyster-like forms which so strongly char- 

 acterize the Marshalltown and the Navesink, some other species 

 should probably be included in the same faunal element, among 

 which are the following species which are as yet known only 

 from these two faunas: Plagiostoma erecta, Unicardiwm um- 

 bonatum, and Odontofusus medians. To these should also be 

 added, in all probability, Trigonia thoracica which has been 

 recognized in both the faunas and also in the intermediate Weno- 

 nah, where, however, only a single occurrence of a single in- 

 dividual has been observed. 



The origin of this Hxogyra element in the Marshalltown fauna 

 of New Jersey is probably from the more southern gulf region 

 where the genus Hxogyra is widely distributed and very abun- 

 dant. Furthermore the stratigraphic position of H. ponderosa, 

 as regards E. costata, is the same in the south as in New Jersey. 



