Species o/" Didy mograpsus. 345 



obtuse radicle, at a primary angle of about 330°, but after- 

 wards curved away from the ratlicle, so as to become nearly 

 horizontal. The angle of divergence of the stipes may there- 

 fore be stated upon the whole as 180°. The stipes are ex- 

 tremely narrow at first, but widen out till a width of one- 



a, Diilymograpstts fascictdatus, from the Skiddaw Slates, restored ; b, a 

 fragment, enlarged. The inclination of the cellules to the axis is too 

 great in these figures, 



twenty-fourth of an inch or more may be attained. The 

 cellules are on the opposite side of the frond to the radicle, or 

 occupy the sides of the angle of divergence. They are ex- 

 cessively long and narrow, about twenty-four in the space of 

 an inch, ciu'ved in accordance Avith the cm-vature of the stipes, 

 overlapping one another for fully two-thirds of their entire 

 length, the cell-mouths being at right angles to the axis. 

 The common canal is extremely narrow. 



The materials in my possession for a diagnosis of this spe- 

 cies are not satisfactory. Those specimens which exhibit the 

 general form of the frond are too ill-preserved for a proper 

 determination of the cellules ; and those which exhibit the 

 cellules are all fragments broken off close to the radicle. I 

 am, however, fully satisfied of the identity of the two sets of 

 specimens, and have therefore ventured to restore the species 

 provisionally, in the hope of shortly obtaining more perfect 

 examples. 



Loc. Upper beds of the Skiddaw Slates : Ellergill, near 

 Milbmui ; Thoniship Beck, near Shap ; and Eggbeck, near 

 Pooley. 



Didymograpsiis gemtmis, His. Fig. 6. 



(See Hisinger, Letha3a Suecica, pi. 38. fig. 3 ; Salter, Quart. 

 Jouni. Geol. Soc. vol. xix. p. 137, fig. 13 c, and Mem. Geol. 

 Survey, vol. iii. pi. 11b. fig. 8; Nicholson, Quart. Joum. 

 Geol. Soc. vol. xxiv. p. 134, pi. 5. figs. 8-10.) 



Frond consisting of two small stipes springing from a long 

 and slender radicle, at an angle of divergence which is primi- 

 tively about 15°. The base is almost always more or less 

 rounded ; and the stipes very rapidly become parallel or sub- 



