Reports tt Proceedings — Geological Society of London. 187 



adductor muscles as the area of the shell increased in height. It, 

 and the transverse plate to which it was attached, originated as a 

 modification of an apical callosity such as existed in many Spiriferoid 

 shells. It was initiated in Middle Devonian times, and reached its 

 acme early in the Carboniferous Period. 



All known species of Syringothyris have the fold in the brachial 

 valve, and the sinus in the pedicle-valve, smooth. Species such 

 as S. distcms, in which the fold and sinus are plicated, do not possess 

 a syrinx, and are incorrectly referred to Syringothyris. 



The form described by McCoy as Spirifera laminosa is referred 

 to a new genus, since it has neither the punctate shell- structure of 

 Spiriferina nor the internal characters of Syringothyris. The 

 genus is represented in the Lower Avonian by mutations of the 

 species laminosa McCoy, and in the Upper Avonian by the species 

 suhconica Martin. 



Syringothyris and Spiriferina are in no way related, either 

 morphologically or phylogenetically. 



The small Carboniferous shells that have hitherto been referred 

 to Spiriferina include two types characterized by external differences. 

 Of these two types, one, in which there are numerous ribs and a 

 relatively large rounded fold and sinus, is relegated to a new genus ; 

 while the members of the other type, which include shells with a 

 few large angular ribs, are for the present retained in Spiriferina, 

 although the type-species of that genus was derived from the Lias 

 The subdivision here suggested for the Carboniferous forms will, 

 it is believed, prove to be applicable to the later species also. 



2. " Jurassic Chronology : I — Lias. Supplement 1, West 

 England Strata." By S. S. Buckman, F.G.S. (Read in the absence 

 of the author by Dr. W. D. Lang, M.A., F.G.S.) 



In this communication the following points are discussed : — 



(1) The Ammonite and some Brachiopod faunas of the Lias of 

 Gloucestershire and Worcestershire. 



(2) A method of faunal plotting as an aid to faunal analysis. 



(3) That in the collection, analysis, and comparison of faunas, 

 the following causes of failure have to be considered : Stratal, 

 Depositional, Faunal, Dispersal, Exposure, Collection, Arrangement, 

 Nomenclature, Fossilization, Preservation, Extraction, Zonalization, 

 Publication ; but several of these are not applicable to results 

 derived from the investigation of limited areas. 



(4) The evidence appears not only to support the conclusions of 

 the author's former paper, but to show that in certain cases a 

 fuller sequence of faunal episodes may be required. 



(5) The fauna of small Ammonites in these Liassic beds, especially 

 that of small Schlotheimice at Gloucester, suggests comparison with 

 the faunas of Hierlatz and Spezia. The use of technical terms 

 for different sizes of organisms, especially for small forms, is briefly 

 illustrated. 



(6) It is suggested that the strata and faunas of these Continental 



