SUB-GENUS HETEROTRYPA. i37 



Monticulipora (Heterotrypa) moniliformis, Nich. 



(Plate I. figs, i-ir.) 



Chcetetes moniliformis, ^\d\o\%ox\, Geol. Mag. Dec. II., vol. i. p. 57, PL IV. 

 figs. 7^, 7/^ 1874. 

 „ „ Nicholson, Palreontolcgy of Ontario, 1874, p. 60, fig. 17. 



Spec. Char. — Corallum dendroid, the branches usually hav- 

 ing a diameter of from three to five lines, or occasionally more. 

 The surface may be nearly smooth, but is usually provided 

 with bluntly rounded tubercles or monticules, which seem to 

 be composed of corallites of a very slightly larger size than the 

 average. The calices are polygonal, and the thick walls be- 

 tween them exhibit at all their angles of junction well-marked 

 blunt spines, which, in slightly worn examples, produce a very 

 characteristically rough superficial aspect. The walls of the 

 corallites are completely amalgamated, and are mostly of tol- 

 erably equal dimensions, averaging i-yoth to i-6oth inch in 

 diameter, thoueh occasional smaller corallites are intercalated 

 among them. There is also a great number of thick-walled 

 hollow spines (" spiniform corallites"), which are of unusually 

 large size, and are placed at almost all the angles of the junc- 

 tion of the normal corallites, as well as often in the substance 

 of their walls. The tabulae are complete, horizontal, or slightly 

 curved, from i-iooth to i-8oth inch apart. 



Obs. — Monticulipora inoniliformis presents itself, so far as I 

 have seen, always in the form of stout branching stems, the 

 surface of which is usually marked by moderately conspicuous 

 rounded monticules (PI. I. fig. i), though these may be want- 

 ing. By examination with a lens, the calices are seen to be 

 polygonal ; and, if the surface be at all worn, their angles 

 of junction always project as very conspicuous nodal spines, 

 which will usually enable the spines to be recognised even by 

 an external inspection (PI. I. fig. ici). 



As regards the internal structure of the corallum, thin tangen- 

 tial sections (PI. I. fig. \li) show a seeming entire amalgamation 



