60 Proceedings of the Royal Physical Society. 



are yet more abundant on one platform than on any other ; 

 and (3) those which are absolutely characteristic of some 

 definite horizon, and are never found either above that or 

 below. For the purpose here in view (1) may be omitted, 

 and (2) and (3) may be treated together. I am much 

 indebted to my colleague, Mr Macconochie, for his friendly 

 help in this and many other matters pertaining to grapto- 

 lites. The list is as follows : — 



C2. 



(c) Rastrites maximiis. 



(b) Jloiiograptus spinigerus, J/, distans, Climacograptus 



noi'malis, Petalograjytus Joliiim. 



(a) Alonograpius clingani, Petalograpius coineta, Mono- 



graptiis creriuLaris, Rastrites j^eregrinus, R. hyhridus. 



C 1. 



(c) Monograptus gregarius^ M. fiinbriatus, M. convolutus, 



M. arge^iteus, M. trutngulatus. 



(b) Dijjlograptus vesiculosus, Mo7iograp)tus cyphus, M. 



tenuis. 



(a) Diplograp)tus acicminatus, Dimorphograptus con/ertus, 



D. elongatus, D. swanstoni. 



B 2, and 1. 



(e) Dicellograptus ancejys, D. truncatus, Diplograptus 

 foliaceus. 



(d) Dicellograptus complanatus, Leptograpiu s Jiaccidus^ 



Diplograptus socialis, Amjyhigrapius diver gens. 



(c) Climacograptus tubuliferus. 



(b) Pleurograptus linearis, Diplograptus quadrimucronatus, 



Dicellograptus forchammeri, D. cliiigani, D. cadu- 

 ceus, Dicranograjytus rainosus, Climacograptus 

 caudatus. 

 (a) Cryptograptus tricornis, Diplograptus rugosus, Lasio- 

 graptus harknessi, Climacogi^ajHus scharenhergi, C. 

 wilsoni. 



A 3, 2, and 1. 



CliTnacograptus bicornis, C. jMlti/er, Hallograptus mucro- 

 natus, Thamnograp)tus typus, Dicranograptus rectus, 



