EXPLANATION OF PLATE XLI. 



Ammonites (Placentacbras) placenta, De Kay (p. 255). 



Figs. 1. Outline of a septum, natural size, from near the outer part of the specimen figured on 



PI. XL, hut from the opposite side. 

 2. View of a small specimen from near Freehold, showing the umhilicus and the lines of 

 nodes at its outer margin. 



Ammonites dentato-carinatus Eoem. (p. 250). 



3,4. Two views of the only fragment of the species linown from New Jersey. Acad. Nat. Sci., 

 Phila. 



Ammonites complexus Hall & Meek (p. 249). 



5,6. Lateral and dorsal views of the only fragment seen from within the State. Acad. Nat. 

 Sci., Phila. 



7. Diagram of a septum as far as it can be traced. 



Ammonites (Sphenodiscus) lbnticularis Owen (p. 258). 



8. View of a fragment from near the umbilicus, representing parts of several chambers of a 



rather large specimen. 



9. View of another fragment from near the dorsal margin of a large specimen. These two 



are all I have seen of the species from New Jersey. 



Ammonites (Placentaceras) tilifer Morton (p. 257). 



10. View of the fragment figured by Dr. Morton in his Synopsis. 



11. View of a larger fragment, also from Dr. Morton's collection, showing the dorsal line. 

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