of the Genus Ptilograpsus in Britain. 241 
e owe to the kindness of Mr. Lightbody, of Ludlow. Its mode 
of branching is much more discrete than that of P. anglicus ; 
and the branches, which arise alternately from opposite sides, 
are not provided with pinnule or cellules near their origins. 
Whether true pinnule are developed on the terminal portions 
of the branches, or not, is doubtful; but both pinnule and 
cellules appear to be present on one of the branches of my 
specimen (see fig. 5). tf this is really the case, then the fossil 
would form a new species of Péclograpsus ; but it is just possi- 
ble that it may be referable to Dendrograpsus, a genus equall 
ancient with the former, and equally unknown in beds of dik 
a late age. 
Besides the above, the Ludlow rocks in the neighbourhood 
of Ludlow contain at least three other species of Graptolites. 
One of these is the familiar Graptolites priodon of Bronn— 
the G. ludensis of the ‘Silurian System.’ ‘The second is cer- 
tainly distinct from G. priodon, though none of the specimens 
at present in my possession are in a state of sufficiently good 
preservation to enable me to come to an accurate determina- 
tion. It is identical with a Graptolite which occurs in the 
“« sheer-bate”’ beds at the top of the Coniston Flags of the 
north of England; and it seems almost, if not quite, undis- 
tinguishable from one of the forms of G. colonus, Barr. (See 
Barrande, Graptolites de Bohéme, pl. 2. fig. 5; Geinitz, 
Graptolithen, pl. 2. fig. 34.) The third presents a considerable 
resemblance to some varieties of G. Nelssont, and also to the 
younger forms of G. sagittarvus, Linn.; but it is remarkable 
for the peculiarity that the cellules are on the concave (instead 
of the convex) side of the stipe. ‘This condition is probably 
of specific value ; but it seems better to refrain from making a 
new species until, by the examination of an extensive suite of 
specimens, the peculiarity in question is proved to be constantly 
_ and persistently present. Whether specifically distinct or not, 
the existence in the Ludlow rocks of a form so closely allied 
to the above-mentioned Lower-Silurian species, along with a 
pe hitherto only known from the base of the Lower Llan- 
eilo series, is a highly suggestive and noteworthy fact. For 
one thing, it seems to be exceedingly probable that the Grap- 
tolitide will ultimately be found to be not so exclusively 
Silurian as has generally been supposed. Hall has taken the 
first step in this direction by the discovery in America of 
opt of Dictyonema in the Old Red Sandstone (Upper 
elderberg and Hamilton groups); and subsequent researches 
will very probably show the coexistence with these of other 
genera of which the Graptolitic nature is more universally 
acknowledged. 
