PAPERS ON GEOLOGY AND GEOGRAPHY 423 



These are similar to the typical Girfyina ventricosa 

 (Meek, von Staff) but are slightly smaller on the aver- 

 age. Considerable variation in size suggests the pres- 

 ence of more than one type, but all variations have been 

 found in one bed. The noteworthy feature in this dis- 

 trict is the apparent restriction of these Fusulinas to a 

 single zone in the geologic section. 



3. Other occurrences in the margin of the Eastern In- 

 terior Basin: 



Besides the localities noted previously, lying in north- 

 western Illinois, Fusulinas have been found farther south 

 near Camp Point in Adams County. The limestone here 

 is an argillaceous rock, similar to that farther north, and 

 the Fusulinas apparently are of the same variety as those 

 in the Bock Island district, and these are tentatively re- 

 ferred to the Girtyina ventricosa type. 



In southern Illinois, Fusulinas have been found in the 

 limestone over what has been called No. 2 coal on Big 

 Muddy Eiver south of Muiphysboro in Jackson County. 

 Apparently the same type of rock and the same type of 

 Fusulina appear here as along the western margin of the 

 State. 



On the eastern margin of the field very little work has 

 been done, although Fusulinas have been found in a dark, 

 argillaceous limestone overlying what appears to be No. 

 6 coal of the Illinois section on the Wabash near Perrys- 

 ville and Cayuga in Fountain County. These occur- 

 rences suggest a continuity of this limestone throughout 

 the Coal Basin. 



4. Occurrences in the interior of the IUi)wis Coa^ Basin: 

 Recent examination of the core from Shelby County 



has shown Fusulinas at two distinct horizons. Girtyina 

 ventricosa appears at its normal position in the limestone 

 over No. 6 coal, and another form resembhig it but of 

 different proportions and a suggestion of different inter- 

 ior structure is found in a more coarsely ciystalline and 

 purer limestone. This stratum lies 530 feet over the 

 No. 6 cap rock and is tentatively correlated with the New 

 Haven limestone of "White Countv. 



