528 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [June 17, 



cesses, which are usually small and short. The central one of these 

 is the proximal extension of the solid axis, and constitutes the true 

 " radicle" or "initial point." The two lateral spines are processes 

 from the first two cellules on either side, and point downwards, 

 diverging from the line of the axis at an acute angle. The distal 

 extremity is truncated, and is limited by a straight line, beyond 

 which the solid axis is prolonged, often for an inch or more, being 

 sometimes slightly dilated. (This dilatation of the distal extremity 

 of the axis must be carefully distinguished from that of D. vesicu- 

 losus, Mch., in which it is much more extensively developed, whilst 

 the other characters of the frond are entirely diflPerent.) The cel- 

 lules are from 20 to 28 in the space of an inch, inclined to the axis 

 at from 40° to 45°, overlapping one another for about one-half of 

 their length, and terminating in broad triangular denticles, usually 

 somewhat rounded at the point. The cell- apertures are at right 

 angles to the axis, or directed slightly upwards, each transgressing 

 for a short distance upon the cellule immediately above. 



The above description is taken mostly from specimens obtained 

 from the Upper LlandeUo rocks of Dumfriesshire ; but the examples 

 from the Coniston Flags do not differ in any important respect, 

 though mostly fragmentary and but indifferently preserved. D. 

 pristis, His., is easily recognized by the peculiar shape of the frond, 

 by the three small processes at the base, and by the characters of 

 the cellules. D. palmeus, Barr., has not unfrequently been con- 

 founded with it ; but the diagnosis between the two is extremely 

 easy when the above characters are attended to. 



Loc. Coniston Flags of Mosedale in Long Sleddale. 



Climacogeapstts (|)iplograpsus) teeetiuscultjs, His. 



Prionotus teretiusculiis, Hisinger, Leth. Suec. Supp. ii. t. 38. 



fig. 4. 

 GraptoUtes personatus, Scharenberg, Ueber Grapt. t. 2. figs. 



17-32. 

 Diplograj>sus rectangulmis, M'Coy, Ann. Nat. Hist. 2nd series, 



vol. vi. p. 271, and Pal. Foss. p. 8, pi. 1. B. fig. 8. 

 Climacograpsus scalaris, Carruthers, Geol. Mag. vol. v. p. 131. 

 Climacograjpsus minutus, Carruthers, ibid. p. 132. 



Frond forming a hollow cylinder, divided into two tubes by a ver- 

 tical septum, and having a row of cellules excavated in its sub- 

 stance on each side. The frond is thus seen to be composed of 

 two simple monoprionidian stipes united back to back, the dorsal 

 walls of the two coalescing to form the median septum, along the 

 centre of which runs the solid axis. The general form of the frond is 

 cylindrical, varying in length from | of an inch up to 2| inches (ex- 

 clusive of the prolongations of the axis), tapering towards the base, 

 and attaining a width of ^ of an inch in the fully developed portion 

 of an adult specimen. The solid axis is prolonged beyond both extre- 

 mities of the frond, often to a very considerable length. The ap- 

 pearances presented by different examples vary according to the 



