1 66 THE GENUS MONTICULIPOKA. 



Otherwise come into direct contact. Tabuke wanting (?) or 

 incomplete (?) in the large coralHtes ; but numerous, closely 

 set, complete, and horizontal in the smaller corallites. 



Obs. — The corallum of this species is almost always found 

 imbedded in the matrix in such a manner that the concave 

 under side, with the striated epitheca, is alone visible (PI. IV. 

 fig. 4), while the convex upper side, carrying the calices, is 

 completely concealed from view. I myself have never seen 

 any specimens save in the condition above mentioned ; but 

 Mr James has described examples in which the upper surface 

 is shown, and he states that these exhibit a series of oval or 

 circular calices, without any monticules or groups of large 

 tubes. The corallum is remarkable for its extreme tenuity, 

 and the resulting shortness of the corallites, and, in all the 

 ordinary specimens, tangential sections can only be prepared 

 by the process of grinding away the thick matrix from the 

 upper side. All the examples that I have seen are deeply 

 concave below, but Mr James states {loc. cif.) that he has 

 seen specimens which are nearly flat. 



As regards the internal structure, tangential sections (PI. 

 IV. fig. ^a) show that the ordinary corallites are divisible into 

 two quite distinct series, intermingled regularly with one an- 

 other. The large tubes are oval in shape, each surrounded 

 by a thin wall, and quite distinct from neighbouring corallites 

 of the same series. As seen in sections of this nature, there 

 is commonly a ring of transparent calcite immediately within 

 the wall, and then the visceral chamber is filled centrally with 

 the dark matrix. The appearance thus produced is similar to 

 what is seen when perforated tabular exist, but the phenomenon 

 is not constant, and is irregular in its development ; while I 

 can find no traces of such incomplete tabular in long sections. 

 The small corallites are more or less angular in shape, occupy- 

 ing the intervals between the large tubes, though never com- 

 pletely isolating these, no more than a single row ever existing 

 between any given pair of the latter. Interspersed with the 

 preceding, and especially occupying the points where the large 



