250 TABULATE CORALS. 



pora. The conversion of the smaller corallites into a mass 

 of lenticular vesicles, and the round form of the larger coral- 

 lites (PI. XI., fig. 4 #), render this resemblance especially 

 noticeable. The large corallites, however, appear to be more 

 markedly free towards their upper ends, and the openings 

 of the smaller tubes upon the surface do not appear to be 

 conspicuous or even recognisable (PI. XL, fig. 4). 



Dr Rominger, in his diagnosis of the genus, adds the 

 further character that the septa are composed of " vertical 

 rows of spinules." This of itself would go far to separate 

 the genus from Plasmopora and Heliolites, in which the septa 

 appear to be always lamellar. 



Genus PINACOPORA, Nich. and Eth., jun., 1878. 



(Mon. Sil. Foss. of Girvan, Fasc. i., p. 52.) 



(PL XII., figs. 3 - 3 ft) 



Gen. Char. " Corallum composite, coin-shaped, of extremely 

 short corallites supported upon the upper convex surface of a 

 free, discoidal, concavo-convex, concentrically striated epitheca. 

 Corallites of two sizes, regularly alternating with one another. 

 Large-sized corallites disposed in obliquely decussating rows, 

 each completely surrounded by a circle of very much smaller 

 corallites (' ccenenchymal tubes'), rarely more than a single 

 row of these latter, however, intervening between any given 

 pair of the larger tubes. Large tubes furnished with twelve 

 short septa, in the form of blunt spiniform projections ; small 

 tubes without septa. Large tubes furnished with one or two 

 tabulae, or rarely more, situated close to their base, the upper 

 portion of the tube being open. Small tubes furnished with 

 from two to four strong and complete tabulae, which extend to 

 close to their summits. Large tubes circular or oval in shape ; 

 small tubes irregular in shape. No mural pores. No colu- 

 mella." 



Obs. The above generic diagnosis is taken from the Mono^- 



