244 O. W. WILLCOX 



chambered types represented in Figs. 2 and 3. Fig. 2 has two unequal 

 and somewhat dissimilar chambers. Fig. 3 shows an end view of a frag- 

 ment of a three- chambered specimen. In Fig. 5 are shown cross- 

 sections of a number of selected specimens. Fig. 6 is a sketch of the 

 projecting ends of a group of concretions as they appeared in the 

 bank of a railroad cut. Fig. 4 is from a photograph of a bluff in the 

 Highlands of Navesink also showing projecting ends. 



In the compound concretions there is usually one primary chamber 

 which is more or less accurately circular in cross-section, and some- 

 times more than one. The cross- sections of the secondary or parasitic 



Fig. I 



chambers are only arcs of circles. It is in fact a notable characteristic 

 of all these concretions, of whatever dimensions or however otherwise 

 irregular, that they show in cross-section practically no other lines 

 than greater or smaller arcs of circles. 



As may be seen from Figs. 5 and 6, the number of secondary 

 chambers in a single specimen may be large. Often in a compound 

 individual the ratio of the dimensions of the primary and secondary 

 chambers is rigidly maintained throughout its observed length, but 

 this is not invariable. Frequently a secondary chamber will end 

 abruptly in a cul-de-sac; just as frequently it will diminish gradually 

 until its wall merges imperceptibly with the wall of its primary, so 

 that a concretion which is compound at one end may dwindle down 

 to a single primary tube at the other. 



A noteworthy but puzzling feature is the fact that, without observed 

 exception, these concretions all occupy a horizontal position, and lie 

 with their longer axes parallel to the strike of the formation, which is 



