1868.] NICHOLSON CONISTON-FLAG ORAPTOLITES. 533 



Though the typical form of G. lohiferus, M'Coy, can be readily 

 distinguished by the above characters, yet it must be conceded that 

 it in some cases approaches so closely to G. Sedgivicldi, Portl., as to 

 render any sharp line of demarcation between the two impossible. 

 This is especially the case in specimens showing fragments of the 

 stipe near the base, in which case an exact distinction is sometimes 

 impossible. Graptolites millijpeda, of M'Coy, does not seem to have 

 been founded on the proximal extremity of G. lohiferus, as has been 

 thought, but upon that of G. Sedgiuiclcii. G. (Jlinganl, Carr., is, 

 however, to be referred to the young form of G. lohiferus, there being 

 in this case a distal extension of the axis, as there usually is in the 

 young of the monoprionidian species. Tlie specimens of G. lohiferus 

 from the Coniston Flags agree in almost all respects with those from 

 Dumfriesshire ; but the cellules seem to be generally rather more 

 closely set. 



Two varieties of G. lohiferus appear to be sufficiently well-marked 

 to deserve distinct names. 



Var. a. Nicoli, Harkn. Quart. Journ. Geol. Soc. vol. vii. pi. 1. 



figs. 5 a, h. 



This form approaches very closely to the normal type, the chief 

 points of diiference being the horizontality of the cellules, and their 

 tolerably uniform breadth, the extremities not forming " obtusely 

 rounded lobes." The number of the cellules is also higher than is 

 usual in the ordinary form, being from 25 to 30 in the space of an 

 inch. This variety occurs commonly in some parts of the Coniston 

 Flags, and seems to be really a variety and not to depend upon the 

 mode of preservation, direction of the pressure, or any other acci- 

 dental circumstance. 



Var. /3. EXiGims, Nich. PI. I. figs. 27, 28. 



This is the form figured by Barrande as the young of G. lohiferus 

 (op cit. pi. 3. fig. 14). It is distinguished by its narrow width 

 (not more than from -^ to -f^ of an inch), by the very slender common 

 canal, and by the shape of the cellules, which have an upward in- 

 clination, are slender at the base, and have the extremity inrolled so 

 as to form a rounded knob. The cellules are about 30 in the space 

 of an inch. 



Log. The ordinary form of G. lohiferus occurs in the Coniston 

 Flags of Skelgill Beck, near Ambleside, and of Mosedale in Long 

 Sleddale ; whilst the former locality yields also the two varieties 

 above described. 



Graptolites Sedgwickii, Portl. PI. XIX. figs. 31-34, PI. XX. figs. 



1, 2, and 28. 



G. convolutus, Hisinger, Leth. Suec. t. 35. fig. 7. 

 G. proteus, Barrande, Grapt. de Boheme, pi. 4. figs. 12-15. 

 G. distans, Portlock, Geol. Ptep. pi. 19. figs. 4 a, 4 6. 

 G. spiralis, Geinitz, Graptolithen, pi. 4. figs. 32-35 ; Barrande^ 

 op. cit. pi. 3. figs. 10-13. 



