508 Dr. H. A. Nicholson and Mr. A. H. Foord on 



FistuUjpora utriculus, Rominger. 

 (PI. XVI. figs. 1-1 e, & PI. XVII. figs. 1, 1 a.) 



Fishdipora tttriculus, Rominger, Proc. Acad. Nat. Sci. Phil. p. 121 

 (1866) [no figures], 



Corallum small, irregular, subramose, hollow, thin, sub- 

 cylindrical or compressed ; varying from ^ millim. to 1 

 millim. or rather more in thickness. The surface is covered 

 with monticules, which take the form of warty outgrowths, 

 whose summits consist of clusters of mesopores. The latter 

 may be seen with a strong hand-lens. 



Under the microscope the surface of the corallum is observed 

 to be minutely granulose (PL XVI. fig. 1 Z»), the granules being 

 apparently the free ends or summits of the walls of the meso- 

 pores. The autopores can generally be seen without a lens ; 

 about four of them fill the space of 1 millim., and, as appears 

 to be always the case, some of slightly larger size occur in 

 the region of the '' monticules " or areas of growth. The 

 mesopores are of the usual angular form. The folds of the 

 autopores are in this species remarkably well developed ; they 

 occupy from one third to one fourth of the circumference of the 

 apertures ; the latter are surrounded by a shallow depression, 

 and their margins are slightly exsert. The outlines of the 

 walls of the mesopores can be very distinctly made out in 

 weathered specimens (PI. XVII. fig. 1). 



In tangential sections the autopores are seen to be of an 

 irregular oval shape and of variable dimensions j the meso- 

 pores are sufficiently abundant to make three or four rows 

 around the autopores. The areas of growth, as already stated, 

 are found to be occupied entirely by the mesopores, and around 

 them the autopores are ranked in three or four concentric rows 

 (PI. XVI. fig. Ic). Longitudinal sections show that the 

 autopores have but few tabula3, while those of the mesopores 

 are abundant and are of the usual vesicular description. 



Ohs. We give some additional figures of this very charac- 

 teristic and interesting species. Fig. 1, PI. XVII., is a micro- 

 scopic view of the slightly weathered surface. It is drawn on 

 the same scale as fig. 1 h, PI. XVI. * (enlarged about forty 

 times), and shows the walls of the mesopores ; the interior of 

 these cells, as well as that of the autopores, being filled with 

 crystalline calcite. Fig. 1 a, PI. XVII., is intended to illustrate 

 the projection of the autopores above the general surface of the 

 corallum and the prominence of the arched lips (folds). 



Dr. Rominger [loc. cit.) has compared this species with two 



* In this figure the walls of the mesopores are not indicated, because 

 they are not visible in this part of the specimen, owing, it would seem, to 

 their uniformity of colour with the rest of the surface. 



