24 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [NoV. 21, 



It must be admitted that the terminology is somewhat objection- 

 able ; but most of the ablest palaeontologists of Europe have agreed 

 upon the term " Infra-lias/' and we cannot do better, now that the 

 upper member of this very natural subdivision occupies the position of 

 a great and special coral-province, than accept it. Considering that 

 the beds which now form the upper part of the Infra-lias in Wales 

 are full of Madreporaria, they may well be termed the Astroccenian 

 beds, on account of the predominance of specimens of that genus. 



An objection may be raised, but cannot be maintained, against 

 separating these beds from the true Lower Lias, on account of certain 

 species being common to both. Doubtful specimens of Gryphoea 

 incurva are now and then met with in the Brocastle beds, and they 

 have been recognized in the ujDper beds in some sections of the Pole 

 de Yeau. One specimen from Brocastle has the laminate fossiliza- 

 tion of the species, and a trace of the lateral groove which pecu- 

 liarizes typical Gryjplicea. 



Ceritliium Semele ranges from the Avicula-contorta zone of France 

 through the whole of the Infra-lias, and is found in the true Lower 

 Lias. There is no doubt that Plicatula intusstriata ranges up- 

 wards into the Lower Lias. The common Pentacrinite * of Ewenny 

 and Brocastle is found also in the Lower Lias. It will of necessity be 

 found that many species considered peculiar to, and characteristic of, 

 strata in one locahty have a greater range in others f. The relation, 

 of the bulk of the species of the Infra-lias and of those of the Lower 

 Lias must be considered, and it is impossible to draw strict and 

 artificial lines to serve the purposes of classificatory geology, since 

 nature has always been progressing and has never stood still. 



The subdivision of the Infra-lias forms part of the great Liassic 

 formation, and does so because there are species which connect and 

 link together the successive beds; but the evidences of unconforma- 

 bility, lithological differences, and of considerable but not perfect 

 palseontological breaks do not permit the Infra-lias to be classified 

 with the zone of A. BucMandit- 



* Pentacrinus tuhermdatus, Mill. A species also found in the Middle Lias 

 is noticed as -well. 



t Terquem et Piette and Martin have given very long Hsts of fossils from 

 the various zones of the "Infra-lias ;" and a comparison of these tabulated lists 

 shows in the most vmequiTocal manner that the same species may have a different 

 vertical range in rocks not very distant, geographically speaking. Thus Monili- 

 valtia Haimei is found in the Ammonites-planorbis zone of Jamoigne, but has not 

 been discovered lower than the highest beds of the A.-angulatus zone in the east of 

 England. Lima gigantea, Desh., and NaufAlus striatus, Sow., will be found to 

 have a very different range from that usually admitted by palaeontologists, who 

 make them distinctive of a special horizon in Great Britain. 



\ Terquem et Piette, in their latest memoir, which is one of the most elabo- 

 rate palieontological works ever produced, give the following results of their 

 analysis of the species of the different zones they had examined (Le Lias in- 

 ferieur de Test de la France, 18C5) : — The Planorbis-zone contained 67 species, 

 of which 9 were special to the zone, and 58 passed upwards. The zone of A. 

 angulatus contained 325 species, of which 58 were noticed in the zone below, 

 and two-thirds pass upwards into the zone of A. bisulcatus {A. Bucklandi). The 

 authors state that this is the result of their own work ; and they refer to the 

 labours of other palaeontologists to prove that the species " reellement caracte- 



