NICHOLSON SKIDDAW GRAPTOLITES. 135 



another for a distance of \ to | an inch. The stipes do not, as a 

 rule, diverge at an angle as large as in the specimen figured by Mr. 

 Salter (Mem. Geol. Survey, vol. iii. p. 331, pi. ii. B. fig. 8), whilst 

 their length may be more than twice as great. The cellules are on 

 the upperside of the frond, or on the side remote from the radicle, 

 but are either not shown at all, or are extremely badly preserved ; 

 the denticles are angular, and the cell-mouths at right angles to the 

 axes. Curiously enough, D. geminus does not appear to occur at all in 

 the Quebec group, though it is such a characteristic Lower-Llandeilo 

 species in Europe. 



Loc. Outerside ; Barff ; Bannerdale Fell, near Mungrisedale. 



13. DiDYMOGRAPSUS PATULUS, Hall, Sp. 



Graptolithus patulus, Hall (Grapt. Quebec Group, p. 71, pi. 1. 



figs. 10-15). 

 Didymograpsus Mrundo, Salt. (Quart. Journ. Geol. Soc. vol. xix. 



p. 137, fig. 13/, and Mem. Geol. Survey, vol. iii. pi. 2. B.fig. 6). 



I am unable to discover any important appreciable difference 

 between the species described under the above names, and am there- 

 fore inclined to believe that they are identical, or are, at most, varieties 

 of the same. The former name appears, as far as I can make out, 

 to have been the first published (Geol. Survey of Canada, Eeport for 

 1857, p. 131) ; and in this case it must be retained, though the other 

 has secured a more general currency*. The only distinction between 

 the two seems to be that in D. Mrundo, Salt., as ordinarily figured, 

 the stipes are not so long as in D. patulus, Hall ; but this is obviously 

 a trivial distinction, and is simply due to the fact that the great 

 majority of specimens are broken. 



The stipes in both D. jpatulus, Hall, and D. Jiirundo, Salt., diverge 

 at an angle of 180° from a small radicle, being at first narrow, but 

 widening out till a breadth of -^ of an inch may be attained. 

 The length of the stipes is often great, being as much as 2| inches 

 in a specimen in my possession from the Skiddaw Slates. The 

 cellules are situated on the upperside of the frond, narrow, and in 

 number from 30 to 34 in the space of an inch in all our British 

 specimens (according to HaU the cellules are from 24 to 26 in an 

 inch ; but I do not think this difference is of specific importance). 

 The denticles are well marked, their tips being produced and almost 

 mucronate. 



Loc. Eggbeck, near TJUeswater; Outerside, near Keswick. 



14. DlDTMOGRAPSrS NITIDT7S, Hall, Sp. 



Graptolithus nitidus, HaU (Grapt. Quebec Group, p. 69, pi. 1. 



figs. 1-9). 

 Also figured but not described by Mr. Salter in the Quart. Journ. 



Geol. Soc. vol. xix. p. 137. fig. 13 d 



This very pretty species is closely allied to the former, though 



* 2>. hirundo, Salt, appears to have been only a MS. species in 1861 (Quart. 

 Journ. Geol. Soc. vol. xix. p. 138). 



