of the Oenus Ptilograpsus in Britain. 241 



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 pinnulee are developed on the terminal portions 

 of the branches, or not, is doubtful ; but both pinnulai and 

 cellules appear to be present on one of the branches of my 

 specimen (see fig. 5) . If this is really the case, then the fossil 

 would form a new species of Ptilograpsus ; but it is just possi- 

 ble that it may be referable to Dendrograpsus^ a genus equally 

 ancient with the former, and equally unknown in beds of such 

 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 occm-s 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 Boh^me, pi. 2. fig. 5 ; Geinitz, 

 Graptolithen, pi. 2. fig. 34.) The third presents a considerable 

 resemblance to some varieties of G. Nilssoni, and also to the 

 younger forms of G. Sagittarius, 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 

 genus hitherto only known from the base of the Lower Llan- 

 deilo series, is a highly suggestive and noteworthy fact. For 

 one thing, it seems to be exceedingly probable that the Grap- 

 tolitidte 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 

 species of Dictyonema in the Old Red Sandstone (Upper 

 Helderberg 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. 



