136 PROCEEDINGS OP THE GEOLOGICAL SOCIETY. 



very much more diminutive. As it occurs in the Skiddaw Slates, it 

 is identical with what Hall has figured as the young form of D. nitidus 

 (Ojo. cit. pi. 1. fig. 1) ; but this should probably be considered a 

 distinct variety, since none of our English specimens appear to agree 

 exactly with the adult B. nitidus figured by Hall. 



The frond consists of two stipes, which diverge from a small 

 pointed radicle, and include between them an angle of 150° to 175°. 

 Hall gives the latter as the average ; but in our specimens it is often 

 as low as above stated ; and it is better to consider the angle of di- 

 vergence variable than to found a distinct species upon this character 

 alone. The stipes vary in length from J to J of an inch, very narrow 

 at their commencement, but widening out until a breadth of ^ to ^ 

 of an inch is attained. The cellules are from 32 to 34 in an inch ; 

 the denticles are well marked and angular, but not produced or 

 mucronate, the cell-mouths being at more than right angles to the 

 axis. 



Loc. Common and very well preserved at Barff, near Keswick. 



15. DroTMOGRAPSus BiPiDirs, Hall, sp. 



Oraptolithus hifidus, Hall (Grapt. Quebec Group, p. 73, pi. 1. 

 figs. 16-18, pi. 3. figs. 9, 10). 



This species is a Quebec form, which I have found in both the 

 upper and lower beds of the Skiddaw Slates, especially in the former, 

 though it is by no means of common occurrence. It approaches 

 closely to D. Murcliisoni, Beck ; but it seems to be separated from 

 the latter by sufficiently good characters. Thus in Didymograjpsus 

 Murcliisoni the base is furnished with a long radicle, and the cel- 

 lules are very much pointed ; whilst in Didymograpsus hifidus the 

 base is round or nearly so, and the denticles are simply submucronate. 

 Further there are no proofs that the stipes in the latter species ever 

 attained the great length and breadth displayed by some specimens 

 of the former. The frond in D. hifidus, Hall, is two-stiped, the 

 " stipes diverging from the small and short radicle, and curving 

 slightly inwards, and thence extending in right lines including an 

 angle of 15° to 20°." The stipes are narrow, expanding above and 

 again contracting towards their extremities, the maximum width in 

 our specimens being about -^ of an inch. The base is usually obtuse 

 and gently rounded, but sometimes assumes a more or less pointed 

 character. The cellules are on the inner or upper side of the frond, 

 long, narrow, and slightly curved, about 34 to 36 in the space of 

 an inch, their apices produced and submucronate. 



Loc. Ellergill, near Milburn (upper beds) ; Eggbeck, near Pooley 

 (upper beds); and Outerside (lower beds). 



16. DrOTMOGEAPSUS SERRATULUS, Hall, Sp. 



Graptolithus serratulus, Hall (Pal. New York, vol. i. p. 274, 

 pi. 74. fig. 5). 



I possess several specimens from the Skiddaw Slates of a species 

 of Bidymografpsus, some of which are certainly referable to the 



