526 PROCEEDrN'GS OF THE GEOLOGICAL SOCIETY. [Juiie 17, 



the other hand, the base consists of a long and tapering radicle, 

 which " gradually becomes continuous with the body of the stipe," 

 whilst the cellules are not more than from 20 to 25 in the space of 

 an inch, are markedly alternate, and terminate in '' toothed and an- 

 gular denticles" (see Geol. Mag. vol. iv. p. 109). 



Loc. Coniston Flags of Skelgill Beck, near Ambleside. 



DiPLOGKAPSFS C0]S^FERTTJS, Nich. PI. XIX. figS. 14, 15. 



Frond in short fragments, tapering towards the base, and about 

 •A- of an inch wide in the fully developed portion. Total length 

 unknown, neither the proximal nor the distal extremities of the 

 frond being exhibited. Cellules from 50 to 60 in the space of 

 an inch, inclined to the axis at an angle of about 45°, the cell- 

 apertures being horizontal or directed slightly upwards. The apices 

 of the cellules are prolonged into long, slender, submucronate tips, 

 though they can hardly be said to be furnished with distinct spines. 



Though the above is only known to me by numerous short frag- 

 ments, and though the characters of the base are nowhere exhibited, 

 I have been compelled to frame a new species for its reception, as 1 

 am unable to make it agree with any form as yet described. In the 

 shape of the denticles it agrees very closely with D. mucronatiis, 

 Hall, and it also presents a certain resemblance to B. palmeus, 

 Barr. ; but it is at once distinguished from both these species by the 

 very great number of cellules in the space of an inch. It is also 

 easily separated from D, mucronatus, Hall, by the great comparative 

 width of the frond. 



Loc. Common in the Coniston Flags of Skelgill Beck. 



DlPLOGEAPSFS TAMARISCirS, Mch. PI. XIX. figS. 10-13. 



Frond diprionidian, slender, of unkno^vn length, and having a 

 breadth of about -^-^ of an inch a little above the base. The 

 base is pointed, and sometimes is provided with a proximal exten- 

 sion of the axis. The common canal is well marked, but is exceed- 

 ingly narrow. The cellules are from 25 to 30 in the space of an 

 inch, alternating very distinctly with one another on the two sides 

 of the frond, free for more than two-thirds of their entire length, 

 inclined to the axis at about 10°, and having their outer margins 

 more or less convex and gibbous. The cell-mouths are at right 

 angles to the axis, or nearly so, and occupy about one-half of the 

 entire breadth of the frond. In specimens preserved in relief, the 

 test appears to be marked with fine transverse striae. 



This pretty little DipTograjpsus is readily distinguished by its 

 small width and pointed base, and by the alternate, curved, cup- 

 shaped cellules, which leave scarcely any common canal, are in- 

 clined to the axis at an extremely small angle, and possess nearly 

 horizontal apertures. I have named it after Sertularia tamarisca, to 

 branchlets of which it presents a considerable resemblance. The 

 specimens in my possession, from the Coniston Flags, are all frag- 

 ments in the neighbourhood of the base ; but I possess more perfect 

 examples from the Upper Llandeilo rocks of Dumfriesshire. 



Loc. Coniston Flags of Skelgill Beck (also in the Upper Llandeilo 

 shales of Duff kinnel Burn, near Wamphray). 



