Pa/con to f(\q-y of Ihc Cinctnuaii Group. i8i 



ties, the bases nearly or quite in contact; monticules arranged 

 in diagonal, intersecting rows, and with an average diameter 

 of two and one-half lines ; calices diamond-shaped or hexa- 

 gonal, graduall)' decreasing in size from -^-^ inch in diameter 

 at the summits, to yyo inch in diameter in the interspaces; 

 interstitial cells and spiniform tubuli absent ; cell walls mod- 

 eratel}' thick, the cells arranged diagonally, but the regularity 

 being slightly disturbed by the increasing size of the cells on 

 the monticules ; longitudinal sections show the cells proceed- 

 ing to the surface with a slight inclination ; walls of medium 

 thickness ; two or three diaphragms in each tube, on lines 

 parallel with the upper surface ; tangential sections show the 

 cell walls are not fused. (Jour. Cin. Soc. Nat. Hist., vol. 2, 

 1880, p. 130, as Chcptetcs clegaiis ; Ibid., as Discotrypa elegans, 

 vol. 6, 1883, p. 164). {Lcptotrypa semipilaris Ulrich, Geol. 

 Sur. Illinois, vol. 8, 1890, p. 457). 



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



Rcjuarks. — This species is similar in many respects to the 

 preceding, but differs in the low, broad monticules, and the 

 variability in size and shape of the cells. It should also be 

 compared with M. arco/aia, to which it bears a great resem- 

 blance. The species described by Mr. Ulrich as Leptotrypa 

 semipilaris does not present enough points of difference to 

 justify a separation from the present form, but in order to 

 permit of comparison, the essential features of the species 

 are given below. 



Leptotrypa semipilaris Ulrich. Corallum small, discoid, 

 lenticular or globose, usually hemispherical ; surface smooth, 

 or with low elevations with clusters of larger cells at the 

 apices; corallites direct, thin-walled; calices subpolygonal, 

 eight in two mm.; tabulae usually wanting, but a few occa- 

 sionally developed near the surface; spiniform corallites 

 moderate in number and size, placed at angles of corallites. 



8. — M. LENS McCoy, 1850. 



Corallum discoidal, concavo-convex, the concavity of the 

 base corresponding to the convexity of the upper surface ; 

 varying in size from less than one-fourth of an inch to one 

 inch in diameter, and from one-half to about one line in 



