36 ME. J. THOMSON ON THE OCCURRENCE OE DIPH YPH YLLTTM 



than fissiparity, and this may occur so that the parent corallite 

 becomes trilobed in transverse outline, and the fission is double 

 instead of single. That this is not a junction of buds can be proved 

 by studying the growth of the septa from the dividing laminae. 



Locality. Lower Carboniferous, Scotland. Kirtle Bridge and Black- 

 ridge, Dumfries. 



Var. etjrcattjm (PI. IV. fig. 2). This variety has slightly smaller 

 septa and wider central space than the type. It does not occur in 

 dense masses. 



Locality. Near Eenwick, Ayrshire and Corrieburn, Dumbarton. 



Diphyphylltjm Blackwoodi, sp. nov. (PI. IV. fig. 3.) 



The corallum is in dense fasciculate masses, with corallites of differ- 

 ent sizes, cylindrical, tortuous, close or not, rarely in lateral contact. 

 Epitheca delicate. Diameter 4 to 6 millim. Fossula with a small 

 primary, often indistinct. Septa 15 to 20, according to the size of 

 the corallite, with a similar number of smaller ones (30 to 40 in 

 all), the larger extending inwards considerably, but leaving a wide 

 central space ; they are very thin and delicate near the equally 

 thin wall, and are stouter and decidedly bilaminate at their junction 

 with the innermost endothecal ring; they may extend beyond that. 

 The smaller septa are short, thin near the wall and thicker near the 

 outer endothecal ring. Acicular points rarely exist — in one corallite 

 out of 14. Endotheca stout between the septa and vesicular ; the 

 inner circle of it is often festooned. A vesicular structure is often 

 seen near the wall in the interseptal loculi. Tabulae large, horizontal 

 in the central area and inclined at the edges towards the underlying 

 tabula ; sometimes bent upwards and then having a relation to the 

 fissiparity, which is both single and double. 



Localities. Auchenmead, Beith, near Eenwick, Ayrshire ; Boghead, 

 Lesmahagow, Lanarkshire. 



Var. approxihatum. (PI. IV. fig. 4.) 



This has the " rods " very frequently developed. 

 Locality. Boghead, Lesmahagow, Lanarkshire. 



In a coral with closer corallites than the last, and which might 

 almost be considered to be a variety of it, the septa of the principal 

 series extend so far inwards, and the endotheca is so much less like 

 internal walls, that I consider it to form a new species : — 



DlPHYPHYLLUM CYLINDRICTJM, Sp. n0V. (PI. IV. figS. 5, 5 A.) 



Corallum in dense fasciculate masses, corallites tall and cylindrical, 

 epitheca thin, with narrow growth-rings. Septa few, 18 to 20 large 

 and as many small, the large passing far in and reducing the 

 dimensions of the central area and tabulae. The small septa extend 

 about one fourth of the distance of the others. The vesicular 

 endotheca is delicate, in two fairly distinct circles in the interloculi, 

 and some delicate inclined stereoplasm occurs. Eissiparity is 

 frequent and is of both kinds ; gemmation also occurs. 



