Paleontology of the Citiciinmti Group. 183 



Remarks. — This is an unsatisfactorily-defined and poorly- 

 illustrated species, and mainly for this reason it is placed here 

 as a separate species. It occurs at Wilmington, Illinois, in 

 connection with species known from Cincinnati, and for 

 this reason and in the expectation of its occurrence in Ohio 

 and Indiana, it is included in this Manual. It would, how- 

 ever, be difficult to recognize from the meager description 

 given by its author. 



10. — M. ARCOLATA Ulnch, 1883. 



Coralluni free, very thin, convex, three lines to one inch in 

 diameter and two and a half lines thick, under surface wath 

 radiating striae, or a few obscure concentric wrinkles ; upper 

 surface celluliferous and with a number of convex or irregu- 

 larly angular spaces, .15 inches in average diameter; at the 

 margin of these spaces the cell apertures are circular, yJtt of 

 an inch in diameter and at the center they are ^V inch in 

 diameter; calices frequently closed by opercula; interstitial 

 spaces with interstitial cells and numerous spiniform tubuli ; 

 in longitudinal sections the tubes are seen to be prostrate for 

 about one half their length and then proceed direct to the 

 surface; walls thin, more or less flexuous; interstitial tubes 

 enlarge rapidly and attain their full diameter at the second 

 diaphragm ; in the proper tubes there are only two or three 

 tabulae and these in the lower part; in the interstitial tubes, 

 however, the tabulae are crowded ; tangential sections show 

 cells to have thin walls ; interstitial spaces have large, usually 

 hour-glass shaped cells, occasionally divided in halves by a 

 faintly-defined wall; comparatively large spiniform tubuli 

 developed in all parts w^here the true cells come into contact. 

 (Jour. Cin. Soc. Nat. Hist., vol. 6, 1883, p. 164, as Aspidopora 

 arcolata) {Diplotrypa patella Ulrich, Geol. Sur. Illinois, vol. 

 8, 1890, p. 458.) 



Locality. — Cincinnati and Oxford, Ohio. 



Remarks. — This species is a very close ally of M. elegans, 

 and in a previous paper by Mr. U. P. James and the author,* 

 it was placed as a synonym of it. It seems best, however, in 



*Jour. cin. Soc. Nat. Hist., vol. 10, 1SS8, p. 165. 



