58 MR. D. DAVIES OlS" THE ECOLOaX OF [vol. Ixxvil, 



Six-Foot, and Two-Foot Nine Seams. It again appears very 

 scantih^ in the Pentre Seam, and is almost absent in the Aber- 

 gork}^ Seam ; but it is more evident in the No. 3 and No. 2 

 E-hondda Seams, 



AiN'NULAEiA. — Is feeble in the Five-Foot Seam, disappears in 

 the Middle Yard Seam, and is very rare in the Upper Yard and 

 Nine-Foot Seams. There were no specimens found in the Six-Foot 

 and Two-Foot Nine Seams ; but a few were found in the Pentre 

 and Abergorky Seams, and they are numerous in the No. 3 and 

 No. 2 Phondda Seams. 



Calamite Stem-Leates. — The narrow linear leaves of Cala- 

 mites were only met with in the Five-Foot Seam and the two upper- 

 most horizons : namety, No. 3 and No. 2 Phondda Seams. 



Calamite-Phragma. — The phragma of CaJamites did not occur 

 in the Five -Foot Seam, very rarely in the Middle Yard Seam, 

 was absent in the Upper Yard Seam, rare in the Nine- Foot and 

 Six-Foot Seams, disappearing in the Two-Foot Nine, Pentre, and 

 Abergorky Seams, and feebly evident in the No. 3 and No. 2 

 Phondda Seams. 



Calamite- Coxes. — These were observed in the three lowest 

 horizons and in the four highest horizons ; but the Nine-Foot, 

 Six-Foot, and Two-Foot Nine Seams yielded no evidence. 



Pal^ostachta. — Absent in the Five-Foot and Middle Yard 

 Seams, rare in the Upper Yard Seam, no evidence in the five 

 succeeding horizons in ascending order, rather frequent in the 

 No. 3, and again becoming rare in the No. 2 Phondda Seam. 



Mtrophtllites. — Weak in the Five-Foot Seam, becoming 

 more abundant in the Middle Yard Seam, with a slight decrease 

 in the Upper Yard Seam and Nine-Foot Seam, very rare in the 

 Six-Foot Seam, absent in the Two-Foot Nine Seam, feeble in the 

 Pentre Seam, abundant in the Abergorky Seam, and becoming less 

 common in the No. 3 and No. 2 Phondda Seams. 



PixxuLARiA. — Entirely absent at the six lower horizons, weak 

 in the Pentre Seam, yielding no evidence in the Abergorky Seam, 

 frequent in the No. 3 Phondda Seam, and becoming reduced in 

 number in the No. 2 Phondda Seam. 



Sphe]S"0PHXLL1tm. — Absent in the Five-Foot Seam, rare in the 

 Middle Yard Seam, no evidence in the five succeeding horizons 

 from the Middle Yard Seam to the Pentre Seam, but well repre- 

 sented in this seam, becomins^ rare as^ain in the Abers^orkv Seam 

 and increasino;- in the No. 3 Phondda Seam ; verv common in the 

 No. 2 Phondda Seam. 



Lepidodeis'deoin". — Very rare in the Five-Foot Seam and Middle 

 Yard Seam, increasing considerably in the Upper Yard Seam, 

 becoming continuously scantier in the Nine-Foot and Six-Foot 



