Dr. II. A. Nicholson on new Species of Graptolltes. 237 



to three lines in length, averaging two lines, clongate-ovatc in 

 shape, tapering towards both extremities, the width in the 

 middle being nearly one line, exclusive of the spines. Base 

 obtusely pointed, with a minute, sometimes double, radicle. 

 Axis apparently not prolonged beyond the distal extremity of 

 the frond. Cellules forty-two in the space of an inch, over- 

 lapping one another for about half their entire length, their 

 lower margins straight, inclined to the axis at an angle of not 

 more than about 'Ib"^^ and having the cell-mouths nearly rect- 

 angular to the axis of the frond. Denticles pointed and fur- 

 nished with rigid straight spines, which are usually directed 

 slightly upwards. 



Out of about thirty individuals of this gregarious little spe- 

 cies, all upon the same piece of shale, no important departures 

 from the above characters are observable. The small size and 

 ovate shape of the frond, the low angle which the cellules 

 form with the axis, the acutely pointed denticles, and the pre- 

 sence of straight spines at the cell-mouths sufficiently distin- 

 guish the species. 



Loc. Upper Llandeilo rocks of Dobb's Linn, near Moffat. 



Diphgrapsus vesiculosus, Nich. PI. XL figs. 14 & 15. 



Spec. char. Frond diprionidian, the celluliferous portion at- 

 taining, in fully grown specimens, a length of from one to two 

 inches, and a breadth of from one-eighth to one-sixth of an 

 inch. The celluliferous margins of the frond are almost pa- 

 rallel till close upon the base, when they converge to form a 

 short obtusely pointed basal process, resembling that of D. 

 pahneusj Barr. In the centre of the frond, in place of the 

 ordinary solid axis of the Diplograpsi, is a tubular body, bor- 

 dered laterally by filiform margins. Whetlier a true solid axis, 

 in the form of a cylindrical filament, is also present, cannot be 

 determined. The axial tube is narrow proximally, but widens 

 out distally till a width of nearly one line may be reached, and 

 on passing finally beyond the celluliferous portion of the frond 

 it is directly prolonged into a long, fusiform, ovate or cylin- 

 drical, vesicular dilatation, which is bordered by strong fili- 

 form margins. This terminal vesicle, at first narrow, attains 

 a width of from one-tenth to one-fifth of an inch, and then 

 contracts to an acuminate apex. The cellules arc in contact 

 throughout their entire length, from twenty-iive to thirty in 

 the space of an inch, inclined to the axial tube at an extremely 

 low angle (about 25"). The cell-mouths are nearly ijandlel 

 to the median line of the frond, and are gently rounded and 

 convex, not forming distinct denticles ; so that the celluliferuus 

 margin of the frond appears simply as an undulating line. 



Ann.d:Marj.N,nut. ►Scr. 4. VolW. 17 



