142 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



23. Geaptolites tenuis, Portl. 



Small stipes occur very commonly in the SMddaw Slates, especially 

 in the upper heds, which appear to be referable to this species. On a 

 closer examination, however, many of these will be found to branch, 

 and they are probably all fragments either of a Dendrograjosus, Hall 

 (which is most probable), or of a Pleurograpsus, ISTich. ; but the spe- 

 cimens are too imperfect to allow of any certain identification. 



Loc. Keswick ; BarfiP ; Ellergill, near Milburn. 



24. Graptolites Nilssoni, Barrande. 



This species is stated by Mr. Salter to occur in the Skiddaw Slates 

 at Braithwaite Brow ; but I have never seen any specimen of it. If 

 this determination does not rest upon a specimen of G. tenuis, then 

 G. Nihsoni is the only simple Graptohte (in the Slates) which would 

 not, as far as is yet known, be easily referred to a compound form *. 



Genus Dendrogeapsus, Hall. 



1 have felt great hesitation in admitting this genus into the list 

 of those represented in the Skiddaw Slates, and have only done so 

 at last on the strength of numerous minute branching fragments, 

 which I have found to occur chiefly in the upper beds of the series. 

 These are always extremely fragmentary and imperfect ; but their 

 mode of branching is most consistent with the behef that they belong 

 to a Dendrograpsus, though more perfect specimens may demonstrate 

 this to be a fallacy. 



The genus Dendrograpsus is defined by Hall as including those 

 Graptolites in which the frond is composed of a strong foot-stalk, 

 which is " subdivided into numerous branches and branchlets, which 

 are but slightly divergent, the whole producing a broad, spreading, 

 shrub-like frond." The genus, with the closely allied Callograpsu^, 

 Hall, is essentially characteristic of the Lower Llandeilo group, both 

 in America and in Britain. 



25. Dendrograpsus HALLiANus,Prout (American Journal of Science, 

 vol. ix.). PL Y. figs. 6 & 7. 



Dendrograpsus furcatula, Salt. (Mem. Geol. Survey, vol. iii. p. 

 331, pi. 11 A. fig. 5.) 



The specimens in my possession, if really referable to Dendro- 

 grapsus, accord most nearly with the characters of the above species. 

 They consist of small, very narrow, branching stipes, dividing in an 

 irregularly bifurcating manner, and always occurring in a frag- 

 mentary condition. The cellules are narrow, inchned to the axis 

 at a very small angle, about 24 in the space of an inch ; the den- 

 ticles conspicuous and angular, the cell-mouths being at right angles 



* Whilst this paper has been passing through the press, I have come across 

 several specimens, from the Skiddaw Slates, of an imdescribed XHdymograpsus, 

 in which the cellules have the characters of G. Mlssoni, Barr. Mr, Salter, 

 therefore, probably founded his determination upon a fragment of this species. 



