CORALS OF THE CINCINNATI GROUP. 207 



tubercles, which are occupied by corallites of the ordinary size or slightly 

 larger. Corallites thin- walled, polygonal, about eight in the space of one 

 line, without minute' interstitial tubuli. 



I feel altogether uncertain as to the correctness of this determination, 

 having seen only a single specimen, and that an imperfect one, which I 

 could refer here. The specimen in question forms a mass about three 

 inches and a half in length and nearly an inch and a half thick, grow- 

 ing upon Ambonychia radiata, Hall. It appears to me, however, that it 

 is impossible to separate this species satisfactorily from C. petropolitanus, 

 unless we are prepared to restrict this latter species entirely to forms 

 which had the base covered with an epitheca, and had a free habit of 

 existence. 



Position and locality : Cincinnati group, Cincinnati, Ohio. Collected by Mr. IT. P. 

 James. 



Ch^tetes mammulatus, D'Orbigny. 



Monticulipora mammulata, D'Orbigny ; Prodr. de Pal^ont., 1850. 



Chsetetes mammulatuB, Edwards and Haime, Pol. Foss. des Terr. Palaeoz., p. 267, pi. 19, 



flgl. 

 Monticulipora mammulata, Edwards and Haime ; Brit. Foss. Corals, p. 265. 



Corallum forming irregular expansions of very considerable size, some- 

 times palmate or lobate, carrying the polypes on both sides. Thickness 

 of the corallum usually varying from two to four lines. Surface cov- 

 ered with well-marked and prominent tuberosities, usually of a rounded 

 or obtusely conical form, the elevation of which varies in different speci- 

 mens. The tubercles are somewhat irregularly arranged, at intervals 

 of one line to a line and a half apart, and they are covered with calices 

 which are very slightly larger than the average, occasionally with some 

 very minute tubes interspersed amongst them. The corallites are sub- 

 equal, polygonal; with thin walls, from eight to ten in the space of one 

 line. Very rarely one or' two very minute calices may be detected at 

 the angles of the average corallites. 



This species represents C. Dalei in the ramose series, but is distin- 

 guished by its mode of growth and its less prominent tubercles. It is 

 further distinguished by its small thin-walled polygonal corallites, the 

 absence of exceedingly minute interstitial tubuli, and the fact that the 

 tubercles are covered with calices, which in general are rather larger 

 than the average. 



With a single well-marked exception, all the examples of this form 

 which have as yet come under my notice are frondescent and lamellar, 



