Qeohgical Society. 483 



PUOCKEDINGS OF LEARNED SOCIEXrES. 



GEOLOCilCAL SOCIETY. 



January 7tb, 1020.— Mr. G. W. Lamplu-h, F.R.S., 

 President, in the Chair. 



The following communications were read : — 



1. ' On Sifrincjothyris Winchell, and certain Car1)oniferous 

 Bi-acliiopoda referred to Spiriferina D'Orbignj.' By Frederick 

 John North, 13. Sc, F.G.S. 



This ijajX-n" is the outcome of a suggestion made in 1913 bj 

 Prof. T. F. Sibly, who pointed out the desirability of an attempt to 

 remove the uncei-tainty which had hithei-to existed in the naming 

 of the British species of Si/riiif/o/hi/ris, and of the Carboniferous 

 Spiriferids possessing a lamellose surface ornament, which it was 

 customary' to refer to Spiriferina because there was no other genus 

 for their reception, although it had long been recognized that few, 

 if any of them, really belonged to that genus. 



After indicating the exact sense in which certain frequently 

 occurring terms are used, and reviewing the history of previous 

 research, the Author discusses the history in Avonian times of the 

 genus St/ri)if/ofhi/ris, and suggests a classitieation of its species. 



Variations due to time, to environmental conditions, and to 

 distribution in space, are recognized, and distinctive names are given 

 to the mutations characteristic of cei'tain horizons. 



The syrinx (it is suggested) was a special arrangement called 

 into existence to control the direction of, and to support the 

 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 S])in- 

 feroid shells. It was initiated in Middle Devonian times, and 

 reached its acme early in the Carboniferous Period. 



All known species of Si/ri/if/ofhi/ria have the fold in the brachial 

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

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

 possess a syrinx, and are incorrectly referred to Syrim/ofJii/ris'. 



The fonn descriljed by McCoy as Spiri/'cro laminoxa is referred 

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

 Spiriferina, nor the internal charactei-s of Syrinyolhifis. The 

 <'enus is rejiresented in the linwcr Avonian by mutations of the 

 S])ecies hiininoxa McCoy, and in the I'pjx'r Avonian by the species 

 svbconica Martin. 



Si/riiif/nf/ii/ris and Spirifrriiia are in no way related, either 

 morj)h()logieally or pliylogcneticaily. 



Tlie snuiU Carboniferous shells that have hitherto been referred 



