THE UPPER CRETACEOUS OF NEW JERSEY 81 



large ammonite Sphenodiscns, which has frequently been collected 

 from this horizon, but has not been observed elsewhere. Another 

 very characteristic species is Trigonia caerulea, which has been seen 

 only in this formation, and almost everywhere the beds furnish 

 numerous crustacean claws probably belonging to the genus Cal- 

 lianassa. A fine exposure of this formation occurs at Tinton Falls, 

 N. J., where this hard bed, 22 feet thick, is responsible for a water- 

 fall in a tributary of the Swimming River, and the name "Tinton 

 beds" may be used to designate the formation. The fauna of the 

 Tinton beds is much more closely allied to the faunas of the beds 

 below than to those above, many of the earlier species being present, 

 while Terebratula harlani, the most characteristic species of the next 

 higher division, has never been observed. 



Judging from their faunas, the three formations — Navesink 

 (including that portion of the underlying sand with the Belemnitella 

 fauna), Red Bank, and Tinton — constitute together a major division 

 of the entire Cretaceous series, comparable in rank with the five 

 formations of the " clay-marl" series, and Clark's name "Monmouth" 

 very nearly expresses the limits of the division. 



The Rancocas division of Clark, if some modification of inter- 

 pretation be admitted, is another natural paleontologic division, 

 characterized by the brachiopod Terebratula harlani, but the later 

 investigations of the New Jersey Survey have thrown much light upon 

 this portion of the Cretaceous section. The Sewell marl rarely 

 contains fossils except at its summit, where a very constant shell 

 layer of about 5 feet thickness occurs, being made up almost exclu- 

 sively of the shells of Gryphaea vesicularis and Terebratula harlani. 

 The Vincentown formation consists in large part of calcium carbonate 

 furnished by immense numbers of several species of bryozoans. The 

 remains of echinoids are also more or less common, and in the past 

 some very fine specimens of these fossils have been found in this 

 formation. The Vincentown fauna, however, is so different from that 

 occurring at the summit of the Sewall marl that, were it not for the 

 relationships of the "yellow sand" fauna, which combines both ele- 

 ments, one would scarcely be justified in including the Sewell and 

 the Vincentown under one larger division. 



In Cook's original classification of the Cretaceous beds of New 



