128 THE GENUS MONTICULIFORA. 



larger growth of J\I. gracilis, James, with which it agrees in 

 all the fundamental characters of its internal structure. 



Horizon and Locality. — Cincinnati Group, Ohio (Cincinnati, 

 Waynesville, «S:c.) 



Monticulipora (Heterotrypa) Andrewsii, Nicholson. 



(Fig. 21, and PI. V. figs, r, \a.) 



Chcetetcs pnkhcUus, Nicholson, Quart. Journ. Geol. Soc, vol. xxx. p. 503, 

 PI. XXIX. figs. 5-5^, 1S74. Pal. Ohio, vol. ii. p. 195, PI. XXI. figs. 



Spec. Char. — Corallum variable in form, but essentially 

 dendroid, usually of sub-cylindrical branches, which have a 

 diameter of from two to six lines, are sometimes flattened and 

 expanded, and sometimes inosculate. Calices polygonal or 

 sub-polygonal, mostly about i-QOth inch in diameter, separated 

 by the much smaller openings of a moderate number of in- 

 terstitial tubes, which are principally developed at the angles 

 of junction of the large corallites. The surface also shows 

 rounded groups or clusters of from five to seven corallites of 

 a rather larger size than the average ; but these clusters, 

 though readily recognised, are not so far elevated above the 

 ireneral level as to constitute reg^ular " monticules." In the 

 centre of the branches the corallites are thin-walled, and poly- 

 gonal in shape ; but their walls become much thickened as the 

 tubes bend outwards to the surface, becoming at the same time 

 completely amalgamated with one another. No " spiniform 

 corallites " are present. The tabulae are always complete and 

 horizontal, and are well developed in all the corallites and 

 throuorhout their entire extent ; but the small interstitial 

 corallites are far more closely tabulate than are the large 

 tubes. 



Obs. — The present species is one which has generally been 

 recognised by American palaeontologists as identical with the 

 M. ptilchella^ Edw. and H., of the Wenlock Limestone of 



