MARYLAND GEOLOGICAL SURVEY 599 



must be retained for the European fossil and d'Orbigny's mortoni sub- 

 stituted for the American. It is the personal conviction of the writer 

 that the two forms are identical, or at least that they cannot be separated 

 on a geographical basis. D'Orbigny's criterion certainly will not stand, 

 i. e., that the American form differs from the European in the presence 

 of five instead of four secondaries between each pair of primaries. The 

 normal number in the American form is four as it is in the European and 

 South Indian, but as in the foreign types this number is occasionally 

 increased to five or reduced to three. The outline and relative proportions 

 vary within rather narrow limits throughout the occurrence, and though 

 there is a suspicion that the maximum diameter may fall a little nearer 

 the median horizontal in the American individuals, this cannot be veri-' 

 fied Avithout the examination of much more material than is available at 

 present. 



Occurrence. MAGOTHY FORMATION. Good Hope Hill, District of 

 Columbia. MATAWAN FORMATION. Post 236, Camp Fox, Chesapeake 

 and Delaware Canal, Post 192, Camp U & I, Chesapeake and Delaware 

 Canal, Delaware. MONMOUTH FORMATION. Two miles west of Dela- 

 ware City on John Higgins farm, Delaware; ? Fredericktown, Cecil 

 County; Waterbury, Anne Arundel County, Maryland. KANCOCAS FOR- 

 MATION. ? NoxontoAvn Pond, Delaware. 



Collection*. Maryland Geological Survey, New Jersey Geological 

 Survey, U. S. National Museum, Geological Survey of India. 



Outside Distribution. Matawan Formation. Merchantville clay marl, 

 Marshalltown clay marl, New Jersey. Monmouth Formation. Navesink 

 marl, New Jersey. Eutaw Formation (Tombigbee sand member). Exo- 

 gyra ponderosa zone, Mortoniceras subzone, Georgia; Russell County, 

 Warrior River and Tombigbee River, Alabama; Tombigbee River, Mis- 

 sissippi. Eipley Formation. Exogyra costata zone, Georgia; Chatta- 

 hoochee River, Alabama ; Wilcox, Pontotoc and ChickasaAv counties, Mis- 

 sissippi. Selma Formation. Exogyra ponderosa zone, Monroe and 

 Prentiss counties, Mississippi; Tennessee. Exogyra costata zone, Tom- 

 bigbee River, Alabama: east-central Mississippi; Lee, Clay and Alcorn 

 counties, Mississippi. Cenomanian. ? Mexico, and England. Turanian. 



