1868.] NICHOLSON C0NI8T0N-PLAG GKAPTOLITKS. 531 



size, its breadth being nearly three times as great as that of the species 

 figured by Hall. I am, however, bound to admit, with the imper- 

 fect materials at present in my hands, that I regard the separation 

 of R. perlatus as a distinct species as simply provisional, since more 

 complete specimens might show that it is a large form of R. venosus, 

 Hall. It is only known to me by a few fragments from the Upper 

 Llandeilo rocks of Dumfriesshire, and by two specimens which I 

 obtained at the base of the Coniston Flags, not 10 feet above the 

 Coniston Limestone. Hall's R. venosus, on the other hand, is from 

 the Clinton group, of Middle -Siluiian age. The occurrence of R. 

 perlatus in tbe Graptolitiferous mudstones at the base of the Coniston 

 - Plags is of importance as serving to connect these beds with the 

 flags of Broughton Moor, which are much higher in the series and 

 contain R. Geinitzianus. Its association, too, with so many unim- 

 peachable Lower-Silurian forms is noteworthy as showing that the 

 genus is in no way characteristic of the Upper- Silurian period. 

 Lastly, it is of interest as corroborating the statement of Hall, that 

 a solid axis is present in some, if not in all the species of Retiolites. 



Log. Coniston Plags of Mosedale in Long Sleddale. Hare in the 

 Upper Llandeilo rocks of Duff'kinnel, near Wamphray. 



Eastkites pekegeinus, Barrande. PL XIX. figs. 23, 24. 



Stipe consisting of a simple linear tube, from which the cellules 

 are given oif more or less nearly at right angles. The proximal 

 and distal extremities are unknown, the specimens hitherto discovered 

 being short fragments, usually curved. The cellules vary in number 

 from 22 to 40 in the space of an inch, and from jL- to J of an inch 

 in length. In shape they are linear, slightly narrower at their 

 origin from the axial tube than towards their distal extremities, 

 and usually impressed longitudinally with a median line. 



The specimens of Rastrites peregrinus from the Coniston Flags 

 present all the characters of the ordinary form. Their occurrence 

 in this formation, along with the cognate R. Linncei, is somewhat 

 noteworthy, no member of the genus, as far as I am aware, having 

 ever before been found in Britain in rocks younger than the Upper 

 Llandeilo. 



Log. Coniston Flags of Skelgill Beck, near Ambleside. 



Easteites Linn^i, Barrande. PI. XIX. figs. 25, 2Q. 



Stipe of unknown length, usually gently curved, and consisting 

 of a delicate axial tube, giving off" long tubular cellules from one 

 side. The axial tube is hair-like, and of greater tenuity, when 

 compared with the size of the cellules, than, perhaps, in any other 

 species of the genus. The cellules are nearly rectangular to the 

 axis, or are directed slightly upwards, from 8 to 12 in the space of 

 an inch, from -^ to more than J of an inch in length, linear, 

 slightly enlarged at their commencement, and tapering gradually to 

 their termination. 



R. Linncei is a Bohemian species, the characters of which are very 

 distinct, being at once recognized by the long, remote cellules, and 



