238 Dr. H. A. Nicholson on new Species of GraptoUtes. 



The external portions of the test appear to have been the 

 strongest portions of the polypary, and are always more 

 strongly defined than the inner. 



The name which I have adopted for this extraordinary spe- 

 cies appears to be somewhat mifortunate, since it seems to 

 have given rise to the ojDinion that the presence of a terminal 

 vesicle is the most important or the sole distinguishing cha- 

 racter of the species. This distal vesicle is sometimes seen, to 

 a limited extent, in D. jjristts, His., and in B. 2yahneus, Barr. ; 

 and in this respect our species is only remarkable in ahvays 

 having the vesicle, and in its very large size. D. vesiculosusj 

 however, is totally and entirely distinct from any other Diplo- 

 gra])sus known to me, and its characters are recognizable even 

 in very small fragments. It is completely separated from all 

 other forms by the following characters : — 1, the parallelism 

 of the celluliferous margins of the frond ; 2, the obtusely 

 pointed, triangular basal process ; 3, the contiguity of the 

 cellules throughout their entire length ; 4, the absence of dis- 

 tinct denticles ; 5, the exceedingly small angle which the cel- 

 lules form with the central line of the frond ; 6, the possession 

 of a median axial tube of considerable width, in the place of, 

 or in addition to, a true solid axis ; 7, the possession of a ter- 

 minal dilatation or vesicle, formed by an expansion of the 

 axial tube. 



This combination of characters cannot be predicated of any 

 other known form, and is sufficient to place the validity of the 

 species beyond reasonable doubt. 



Loc. Upper Llandeilo rocks of Dobb's Linn and Frenchland 

 Burn, near Motfat. Rare in the mudstones of the Coniston 

 series, Skelgill Beck, near Ambleside. 



Climacograj)sus innotatus^ Nich. PI. XI. figs. 16 & 17. 



Sj[)ec. char. Frond diprionidian, from three to five lines in 

 length, and little more than half a line in width in its fully 

 developed portion. Base pointed, with a minute radicle. Axis 

 prolonged beyond the distal extremity of the frond. Cell- 

 wpertures forming rounded notches, sunk below the general 

 margins of the frond, and from twenty-eight to thirty-five in 

 the space of an inch. The projecting portions of the frond 

 between the notches formed by the cell-mouths are somewhat 

 quadrangular, with the angles rounded oft'; and from the infe- 

 rior angle of each arises a short stout spine, which is directed 

 horizontally over the mouth of the cellule below. 



This species agrees with CAimacograpsus tgpicah's, Hall, in 

 tlie possession of spines ; but it is altogether a nnich smaller 



