172 SILURIAN RADIATA. 



Palceopora suhtilis (M^Coy). 

 Sp. Char. Corallum forming cylindrical branches, usually 1|^ to 

 2 lines in diameter ; large stellular tubes about one-sixth of a 

 line in diameter^ and a little more or less than their diameter 

 apart ; polygonal intervening tubuli invisible to the naked ej'fe, 

 usually five between adjacent cell-tubes, or about thirty in the 

 space of 1 line ; three cell-tubes with their intervening tubuli 

 in a space of 1 line ; main tubes often weathering as separate 

 sulcated columns. 



In the middle of the branches the cell-tubes seem to be 

 parallel and vertical, but diverge rapidly at the circumference to 

 reach the surface ; they are very often weathered as separate tu- 

 buli, as in P. subtubulata and P. tuhulata, and on the other hand 

 they often break away from casts of the surface, leaving so little 

 trace among the intervening tubuli, that the surface seems merely 

 shagreened under the lens, bearing some resemblance to the 

 Ptilodidya (Stictopora) fucoides (M'Coy), but the casts of the 

 cells are polygonal instead of oval, and far more minute in the 

 present coral. The extreme minuteness of the parts of this spe- 

 cies distinguishes it easily from the P. subtubulata, to which alone 

 it has any affinity. 



Very common in the fine sandstone of Mulock, Dalquorhan, 

 Ayrshire. 



[Col. University of Cambridge.) 



Fistulipora decipiens (M'Coy). 

 Sp. Char. Corallum forming hemispherical or subcylindrical 

 masses 3 or 4 inches in diameter, concentrically wrinkled at 

 base; cell tubes straight, subparallel, with moderately thick 

 walls, leaving clearly defined circular smooth-edged cells in 

 the transverse section, very regular in size and disposition, 

 usually slightly less than half a line in diameter, and avera- 

 ging rather less than their diameter in the shortest line between 

 adjacent cells, in which line there are usually two, or more 

 rarely three, of the intermediate vesicular cellules; about 

 eighteen of the intermediate or polygonal cellules in the space 

 of 2 lines; diaphragms in the small tubes slightly more or 

 less than their diameter apart, two interdiaphragmal spaces 

 in the large tubes slightly exceeding the diameter. 



So exactly does this resemble the Palaopora interstincta (Wahl.), 

 that I have little doubt it has often been confounded with it, 

 although an attentive examination will show that the distinctly 

 walled tubes are smooth within and perfectly destitute of lamellae. 

 I have seen this coral also in large masses in the Upper Silu- 

 rian limestone of Gothland. It may be distinguished from the 

 very nearly allied Manon [Fistulipora) cribrosa (Gold, sp.), by 



