1868.] NICHOLSON CONISTON-FLAG GRAPTOLITES. 539 



approach very closely to, if they do not agree exactly with, the 

 description of O. tenuis by Portlock ; but an examination of a large 

 series of specimens shows that these should really be referred to 

 G. Nilssoni, into the tyjncal form of which they pass by insensible 

 gradations. The above characters arc founded on specimens both 

 from the Coniston Flags and from the Upper Llandeilo rocks of 

 Dumfriesshire, which, if not fragmentary, are certainly distinct, 

 though I am not in a position to assert that they agree exactly 

 with the characters of G. tenuis, Portl. The G. tenuis figured by 

 M'Coy (Pal. Eoss. pi. 1 B. figs. 4, 5) appears to be in reality the 

 young form of G. Sagittarius, Linn. 



Loc. Duffkinnel Burn near Wamphray, and Dobbs Linn near 

 Moifat. 



Graptolites disceetus, Nich. PI. XX. figs. 12-15. 



Stipe long, linear, and slender, commencing by a long, narrow, 

 and gently curved base ; length unknown ; breadth from -^ to 

 ^ of an inch in the fully developed portion of the stipe. Axis 

 exceedingly fine, and sometimes prolonged beyond the distal ex- 

 tremity of the stipe. Common canal of great breadth, occupying 

 about two-thirds of the entire width of the stipe. Cellules very 

 remote, from 12 to 16 in the space of an inch, each resting directly 

 upon the mouth of the one immediately below. Cell-mouths short, 

 forming an oblique aperture running for a short distance across the 

 body of the stipe, the inferior lip being prolonged into a long' 

 flexible, submucronate extension, which is usually directed upwards. 

 The '^superior" cell-wall is apparently wanting, the "inferior" 

 margin being nearly parallel with the axis, straight or slightly con- 

 vex, and from twice to three times as long as the cell-mouths. 



The long, submucronate extremities of the cellules are often fur- 

 nished with little ovoid, or triangular, vesicular bodies depending 

 from their apices (PI. XX. fig. 15). 



This remarkable Graptolite difi'ers to a marked extent from all 

 other described forms, being distinguished by the very remote and 

 distant cellules, almost parallel with the axis, by the great compa- 

 rative width of the common canal, and by the extended, submucro- 

 nate denticles. These peculiarities deprive it of even a distant 

 resemblance to any species with which I am acquainted. The little 

 triangular or bell- shaped vesicles, which depend from the apices of 

 many of the cellules, are so constant in their occurrence and posi- 

 tion, that they cannot possibly be regarded as accidental. They 

 may possibly be reproductive, and may correspond to the " ovarian 

 capsules" of the Sertularidce ; but I have no data whereby to decide 

 this point positively. 



Loc. Coniston Flags of Mosedale in Long Sleddale, abundant and 

 well preserved. 



Graptolites Bohemicus, Barr. PI. XX. figs. 22-24. 



G. Bohemicus, Barrande, Grapt. de Boheme, pl. 1. figs. 15-18. 

 Stipe simple, monoprionidian, of unknown length, and attaining 



