1 8 CREfTACEOUS' PALEONTO'LOGY. 



Lower Marl (Navesink), Red Sand (;Redbank), and Middle 

 Marl (Hornerstown) beds were traced 'from Crosswicks Creek 

 southwest to Rancocas Creek. It was then found that the 

 Red Sand pinched out 2 or 3 miles southwest of Crosswicks 

 Creek, thus bringing' the Lower and Middle Marls in juxtaposi- 

 tion from a point near Jobstown to Salem. Locally, the litho- 

 loigical peculiarities of the Lower Marl were recognizable in the 

 lower part of the combined bed and those of the Middle Marl in 

 its upper portion, but it was not possible to^ map them as separate 

 beds, and there were some facts which indicated that the Lower 

 Marl became proigressively thinner sO'Uthwest oi Marlton, so that 

 more and more oif this horizon was made up of the Middle Marl 

 bed. 



The mistaken identification of the Marshalltown of the south- 

 em district with the Lower Marl northeast of Jobstown natur- 

 ally led to the erroneous correlation of the Middle Marl,. Red 

 S'and and the Wenonah Sand of Crosswicks Creek with the 

 combined Middle and Lower Marl bed, the Wenonah sand and 

 the Englishtown (Columbus) sand, respectively, of Rancocas 

 Creek, and the mistaken correlation was continued on the maps 

 southwest tO' the Delaware Bay. 



That a mistake should have been made in the earlier work is 

 not surprising when it is remembered that accurate topo'graphic 

 maps were not available when the work was done, and that the 

 Marshalltown bed in the southern counties was once dug for marl, 

 and is there much like the Lower Marl ( Navesink) . 



This error of correlation was discovered by the writer as 

 above mentioned in the spring and summer of 1894. In his sec- 

 ond report of progress,^ Dr. Clark very naturally made the same 

 error, since his work up to that time in the region south of Cross- 

 wicks Creek had been in the nature of reconnaissance only and 

 had not been sufficiently detailed to reveal the mistake, which 

 was corrected in his report several years later.^ The repetition 

 of this error in 1893, however, was more unfortunate in that 

 at that time the name Rancocas was proposed (and has been 

 used since by many writers for Cook's Middle Marl and Lime- 



'■ Annual Report of the State Geologist for 1893, p. 353 et. seq. 



„1 -D 



