On the Monticulipoioid Corah of tJie Cinci)i)iati Group. 29 



junction of cells, and projecting as quadrangular i)rocesses above 

 the general level. Interstitial cells more or less numerous. 



Obs. This species seems to be a variable one. Certainly the 

 forms described under different names are not sufficiently distinct 

 to be recognized. Dr. Nicholson says of his D. attrita, that it "is 

 very probably identical with the type species £>. aspera Ed. & H."*. 

 Mr. Ulrich says in his remarks on the genus Dekayia, " On account 

 of their simplicity of structure, inexperienced collectors will prob- 

 ably find some difficulty in distinguishing one from the other, 

 [referring here to five new species he is about to name and des- 

 cribe]. It must, however, be borne in mind that the more simple 

 these organisms are, the more important are their variations. In 

 separating them from each other, the characters principally to be 

 taken into consideration are the following : The growth of the 

 zoarium [corallum]; the size of the cells, and the thickness of iheir 

 walls; the presence or absence of small (interstitial?) cells, — and 

 their distribution if present : the size and number of the spiniform 

 tubuli [corallites]: and lastly the disposition and number of the 

 diaphragms [tabulae] crossing the tubes. "f All these are too 

 indefinite in character and too inconstant in occurrence to serve 

 even for specific characters. His own remarks on D. attrita, wil^ 

 serve to illustrate this fact, and to show how the features change on 

 different parts of the same corallum. " Until lately I was under the 

 impression that Nicholson's D. attrita might be advantageously 

 regarded as a distinct variety of D. aspera, but the material now 

 at hand proves this view untenable. Dr. Nicholson's specimens 

 undoubtedly represent the terminal branches of a typical example 

 of Edwards and Haime's species, the branches of that portion of the 

 zoarium [ corallum ] always being more strictly dendroid and of 

 smaller size than the primary ones. "J; 



Formation and Locality. Lower Silurian, Trenton Group, 

 Biirgin, Ky. Hudson River Gr. , Wisconsin. Cincinnati Gr. , 

 Cincinnati, Loveland, O., Covington, Ky., etc. 



Sub-genus B. 



CoNSTELLARiA, Dana, i8^6. 



Expl. Exp. Zoophytes, 537,1846. Nicholson Pal. Tab. Cor. 

 300, 1H79; Genus Montic. 97,1881; Ulrich, Jour. Cin. S. N. 

 Hist. V, 155, 1882; VI, 265, 1883. 



*Pal. Tab. Cor. 298 



-{•[our. Cin S. Nat. Hist. W. 149. 



^Ibid. VI. 149. 



