60 MR. D. DATIES OX THE ECOLOGT OF [vol. Ixxvil^ 



in the Abersrorkv Seam, increases in number in the Xo. 3 Rhondda 

 Seam, but is rarely found in the Xo. 2 Ehondda Seam. 



Pecopteeis. — Absent at the three lowest horizons, scantr in 



the Xine-Foot and Six-Foot Seams, absent in the Two-Foot Xine 

 Seam, extremelv rare in the Pentre Seam, absent in the Abersrorkv 

 Seam, and very rare in the Xo. 3 and Xo. 2 Rhondda Seams. 



Alzthopteeis. — Pai-ticularly abundant in the Five-Foot Seam, 

 extremely rare in the Middle Yard Seam, absent in the Vpper 

 Yard Seam, very rare in the Xine-Foot and Six-Foot Seams, 

 absent in the Two-Foot Xine and Pentre Seams, very scanty in 

 the Abergorky Seam, disappearing in theXo. 3 and Xo. 2 Rhondda 

 Seams. 



Ceossotheca. — This genus was not observed at any horizon 

 below the Xo. 3 Rhondda Seam, and at this point was exti-emely 

 rare. The specimeng found in the Xo. 2 Rhondda Seam were ten 

 times more numerous than those found in the Xo. 3 Rhondda Seam. 



Eeemopteeis (r). — Absent at the seven lowest horizons, very 

 rare in the Abersrorkv Seam, rather common in the Xo. 3 Rhondda 

 Seam, and absent in the Xo. 2 Rhondda Seam. 



Rachis of Feexs oe Feexlike Pla>'ts. — Scanty in the 

 Five-Foot Seam, common in the Middle Yard and Upper Yard 

 Seams, very uncommon at the succeeding horizons, more frequent 

 in the Penti-e Seam, rarer in the Abergorky Seam, common 

 acjain in the Xo. 3 Rhondda Seam, but decreasincr in number in 

 the Xo. 2 Rhondda Seam. 



Cyclopteeis (Scale-leaves). — Absent at two horizons, namely, 

 the Middle Yard and Two-Foot Xine Seams, always rare at the 

 other horizons, with the exception of the Six-Foot Seam, where it 

 is common. 



Seeds (possibly of a Pteridospermous nature . — These were 

 only found at the three lowest horizons. 



Coedaiie-Leaves. — -Yery prevalent in the Five-Foot Seam, 

 where they easily dominate the other genera of plants. They are 

 verv feeble in the Middle Yard Seam, are well disti'ibuted in the 

 Fpper Yard and Xine-Foot Seams, with a slight decrease in the 

 Six-Foot Seam, prominent again in the Two-Foot Xine Seam, 

 reduced in number in the Pentre Seam (but even here they are 

 abundant). They become considerably scantier in the Abergorky 

 Seam, commoner in the Xo, 3 Rhondda Seam, and diminish in 

 number in the Xo. 2 Rhondda Seam. 



Steexbee&ia (pithcast). — Yery rare thi'oughout; absent in the 

 Middle Yard and Six-Foot Seams. 



Samaeopsis. — Absent in the Five-Foot and Middle Yard Seams, 

 extremely rare in the Upper Yard and Xine-Foot Seams, absent 



