part 1] THE WESTPflALiAN, ETC. O'F EAST GLAMOEGAN. 59 



Seams. In the Two-Foot Nine Seam, Lepidodendron suddenly 

 becomes the dominating genus, and continues in this state of 

 superiorit}^, but in a less degree, in the Pentre Seam. It after- 

 wards disaj)pears in the Abergorky Seam, and in the No. 3 and 

 No. 2 Rhondda Seams. 



SiGiLLARiA. — Similarly to Liepidodendron this genus passes 

 upwards through the different horizons, the two genera increasing 

 and diminishing in number simultaneously : the only difference 

 noticeable being the numerical preponderance of Lepidodendron 

 over Sigillaria in each case. 



BoTiiRODEjfDROisr. — liarc, found only at one horizon : that is, 

 the Pentre Seam. 



Lepidophloios. — Very rare, found in the Pentre Seam only. 



Lkpidostiiobus. — Absent in the Five-Foot and Middle Yard 

 Seams, rare in the Upper Yard and Nine-Foot Seams, not found 

 in the Six-Foot Seam, common in the Two-Foot Nine and Pentre 

 Seams, very rare in the Abergorky and No. 3 Khondda Seams, 

 and absent in the No. 2 Rhondda Seam. 



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

 rare in the Upper Yard and Nine-Foot Seams, absent in the Six- 

 Foot Seam, common in the Two-Foot Nine and Pentre Seams, 

 very rare in the Abergorky and No. 3 Hhondda Seams, and absent 

 in the No. 2 Ilhondda Seam. 



Neuhopteris. — Fair distribution in the Five-Foot Seam, feeble 

 in the Middle Yard Seam, abundant in the Upper Yard and 

 Nine-Foot Seams, still increasing in number and reaching the 

 maximum in the Six-Foot Seam, nearly absent in the Two-Foot 

 Nine, Pentre, and Abergorky Seams, regaining its vitality with a 

 strong representation in the No. 3 and No. 2 Phondda Seams. 



Spheis'opteris. — Persistent, but not so numerous as Neuro- 

 pteris, only once dominating the latter genus (that is, in the 

 Middle Yard Seam), common in the Middle Yard Seam ; then it 

 gradually diminishes at the other horizons until the Two-Foot 

 Nine Seam is reached, where it is absent. Splienopteris appears 

 scantily in the Pentre and Abergorky Seams, very prominently in 

 the No. 3 Phondda Seam, but decreases markedly in the No. 2 

 Rhondda Seam. 



Mariopteris. — This genus, like Sphenopteris, is rather per- 

 sistent, although few specimens were found. It appears scantily 

 in the Five-Foot Seam, is absent in the Middle Yard Seam, very 

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

 very rare in the Six-Foot Seam and the Two-Foot Nine Seam. 

 The Pentre Seam shows it at its maximum of distiibution, and 

 here it dominates the other genera of its class. It is rather rare 



