Paleontology of the Cincinnati Group. 191 



17. — M. BRiAREA Nicholson, 1875. 



Corallum free, dendroid, beginninj^: with a pointed base and 

 expanding above ; branches variable in number, two and one- 

 half to four lines in diameter, cylindrical, possibly branching 

 more than once ; surface smooth ; calices of one kind only, 

 oval or circular; walls of corallites thick at the surface; 

 interstitial tubes and spiniform corallites wanting ; in the 

 axial region the corallites are thin-walled and polygonal ; 

 tabulae complete and horizontal in both axial and peripheral 

 regions, but most numerous at the point where the corallites 

 bend outward toward the surface ; tangential sections show 

 corallites to be uniform in size and of one kind only ; axial 

 sections show thin-walled and polygonal corallites, the walls 

 beginning to thicken when curving outward. (Pal. of Ohio, 

 vol. 2, 1875, p. 202; Nich., Genus Montic, 1881, p. 198.) 



Locality. — Cincinnati, O., and Frankfort, Ky. 



Remarks. — This is one of the best marked species of the 

 genus. It has an apparently free, pointed base, and branches 

 in a digitate manner. The ordinary specimens are from one 

 and one-half to two inches long, but specimens may attain a 

 length of six inches. Specimens from near Frankfort, Ky., 

 present all the characters of the Ohio form, and occur either 

 in the lowest beds of the Cincinnati rocks or in the topmost 

 layer of the Trenton. 



18. — M. GRACILIS (James) Nicholson, 1874. 



Corallum dendroid, branches cylindrical or sub-cylindrical, 

 from less than one line to three lines or more in diameter, 

 branching at intervals ; surface smooth ; calices oval, their 

 long axes corresponding with the long axis of the branch, 

 opening obliquely ; cell mouths greatly thickened ; intersti- 

 tial tubes moderate in number ; spiniform corallites present, 

 but mainly to be detected by microscopic sections ; in the 

 axial region corallites vertical, thin - walled and polygonal 

 with few or no tabulae ; as they bend outward toward the 

 surface the walls become greatly thickened, and the tabulae 

 are more numerous, in all cases being horizontal and com- 

 plete ; three distinct types of corallites are to be recognized ; 



