74 STUART WELTER 



a portion of the Wenonah sand. In his faunal lists Clark does not 

 differentiate the fauna of the Crosswicks clays from that of the Haz- 

 let sand, but gives a single generalized list of species as the fauna of 

 the whole Matawan. As a matter of fact, there is considerable 

 community of characters among the faunas of all five formations 

 recognized by Knapp in the "clay-marl" series, except only the 

 fauna of the upper beds of the Wenonah sand in the southern portion 

 of the area, enough, at least, to make their inclusion in one major 

 division fully justifiable. The two cephalopod genera, Placenti- 

 ceras and Scaphites, characterize the whole series of beds, either one 

 or both being present at every locality where fossils have been exten- 

 sively collected, while neither of them has been detected in the higher 

 beds. There are, however, sharp distinctions between the faunas 

 of the successive formations recognized by Knapp, and these faunal 

 characters are easily recognizable throughout the whole extent of 

 the beds across the state, wherever fossils have been found. In the 

 discrimination of these faunal zones of the "clay-marl" division, 

 however, it is not safe to assert that any particular species is absent 

 from any one of the faunas, and bare lists of species, without some 

 statement of the abundance of the forms noted, might not in all cases 

 show the characteristic features of the different faunules. The 

 combined faunas of the whole series of formations, and even including 

 those to the summit of Clark's Monmouth division, really make 

 one unit of a larger order. The constant recurrence of various 

 species and groups of species, in this entire series of faunal zones, 

 indicates that somewhere along the Atlantic border they lived con- 

 tinuously. As local conditions of environment changed from time 

 to time, the dominant characteristics of the local faunas changed, 

 and it is such changes, for the most part but not wholly, that are 

 recorded in the faunas of these New Jersey formations. 



The Merchantville clay is characterized by the abundance, among 

 other species, of Axinea mortoni, Idonearca antrosa, Trigonia eufau- 

 lensis, and Panopea decisa. In the Woodbury clay these same 

 species are conspicuous for their absence or great rarity. In a collec- 

 tion from the Woodbury clay in Monmouth County, including sixty 

 or more species and many hundreds of individuals, a single specimen 

 of Idonearca and a single Axinea mortoni were found; while, on the 



